Programmatically Remove other products when a particular product(s) is being added to cart, also add a force sell product(s) attached to it. More info here: https://woocommercecommunity.slack.com/archives/C1K9K3UD9/p1599861910188600

_product_sorting_weird_fix.php

<?php
// This was added, cause the envrionment with WooCommerce and WooCommerce Subscription acted weird 🥴.
$pekky_callback_func_name = 'pekky_2_remove_cart_item_before_add_to_cart';

add_filter( 'woocommerce_add_to_cart_validation', $pekky_callback_func_name, 20, 3 );
// Works, different method, faster 😎
function pekky_2_remove_cart_item_before_add_to_cart( $passed, $product_id, $quantity ) {

	// Sample values: array( 23,45,43 );
	$stand_alone_products = [660];//array( 25221, 29237 ); //stand alone products
	$other_products       = [226];//array( 28745, 28746, 28747, 28748 ); // friendly products that can stay in the cart with others
	
	/**
	 *  Products attached to the standalone products
	 * These should be added to cart when a standalone product is in the cart.
	 *  patterns [{standalone_product_id} => array({force_sells_ids})]
	 */ 
	$force_sells_products = array(
		'660'=>[225,229],//'29237' => array( 25556 ),
		'25221' => array( 29234, 29444 ),
	); //products attached to one of the stand alone products
    
	// Add only level 2 or level three program to the cart.
   if ( in_array( $product_id, $stand_alone_products ) ) {
	   // echo "<br>Standalone<br><br>";
		_pekky_sort_stand_alone_products( $product_id, $stand_alone_products, $force_sells_products );
	}
	// Allow other products to be in cart together.
    else if ( in_array( $product_id, $other_products ) ) {

		// Make sure stand alone products aren't in the cart.
		foreach ( $stand_alone_products as $p_id ) {
			// Is this standalone product in the cart?
   			if ( in_array( $p_id, array_column( WC()->cart->get_cart(), 'product_id' ) ) ) {
				// echo "<br>Otherrrrrr producccts<br><br>";
				// Product is there, remove.
				_pekky_sort_stand_alone_products( $p_id, $stand_alone_products, $force_sells_products, false );
			}
		}
        // WC()->cart->add_to_cart( $product_id );
	}
	return $passed;
}

/**
 * Sorts the stand alone products
 * 
 * @param int $product_id
 * @oaram array $stand_alone_products
 * @param array $force_sells_products Products attached to the standalone products
 * These should be added to cart/removed when their standalone product is in the cart/removed.
 * Patterns [{standalone_product_id} => array({force_sells_ids})]
 * @param bool $add_to_cart (optional) true, add to cart, if false, removes, default is true.
 * @return bool false if empty field, true otherwise 
 */
function _pekky_sort_stand_alone_products( $product_id, $stand_alone_products, $force_sells_products, $add_to_cart = true ){
	if ( empty( $product_id ) || ( empty( $stand_alone_products ) || !is_array( $stand_alone_products ) )
	|| ( empty( $force_sells_products ) || !is_array( $force_sells_products ) ) ){
		return false;
	}
	//var_dump("yhhhhh<br><br>");
	$wc_cart = WC()->cart;
	$cart_func = 'remove_cart_item';
	if ( $add_to_cart ) {
		$cart_func = 'add_to_cart';
		// empty cart.
		$wc_cart->empty_cart();
	}
	$p_id = ( $add_to_cart ? $product_id : $wc_cart->generate_cart_id( $product_id ) );
	// var_dump("<br><br>".$cart_func);
	// var_dump("<br>product_id:".$product_id."<br>");
	// var_dump( "<br>function executed: ");
	if( ! $add_to_cart ){
		$wc_cart->{"{$cart_func}"}( $p_id );
	}
	// get list of standalone product id
	$product_force_sells_list = $force_sells_products[$product_id];
	//var_dump($product_force_sells_list);
	
	if( empty( $product_force_sells_list ) ){ 
		// wrong list
		return false;
	}

	// Also add the force_sells product to cart/remove
	foreach ( $product_force_sells_list as $_id ) {
		// var_dump("<br>Force_sales product id: " .$_id);
		$p_id = ( $add_to_cart ? $_id : $wc_cart->generate_cart_id( $_id ) );
		// var_dump("<br> function_exec:");
		$wc_cart->{"{$cart_func}"}( $p_id );
		//reset quantity to 1
		if( $add_to_cart ) {
			$cart_item_key = $wc_cart->generate_cart_id( $p_id );
			$wc_cart->set_quantity( $cart_item_key, 1 ); // Change quantity
		}
	}
	return true;
}

sort_cart_products_with_force_sells.php

<?php
/**
 * 2 functions which do the same thing in different ways
 * 1 tends to run faster than the other (method 2)
 * There's also a function just to monitor runtime spead between the 2 funcs, check properly.
 * 
 * Should be added in your theme's functions.php file or anywhere you put code snippet :)
 * Enjoy at your risk.
 */
$pekky_callback_func_name = 'pekky_speed_remove_cart_item_before_add_to_cart';

add_filter( 'woocommerce_add_to_cart_validation', $pekky_callback_func_name, 20, 3 );

// Monitor runtime speed for first and second method., this should not be used in a live site 🙃.
function pekky_speed_remove_cart_item_before_add_to_cart( $passed, $product_id, $quantity ) {
	$_p_runtime = 0;
	echo "<br>time for 1st function";
	// Monitoring speed runtime the local way :)
	$before = microtime( true );
	pekky_1_remove_cart_item_before_add_to_cart( $passed, $product_id, $quantity );
	$after = microtime( true );

	$_p_runtime = ( $after - $before );
	$first_func = $_p_runtime;
	echo "<br>End of 1st function<br>";
	echo "\nTime frame: " . ( $_p_runtime );
	#############################################
	echo "<br><br>Time of 2nd function";
	// Monitoring speed runtime the local way :)
	$before = microtime( true );
	pekky_2_remove_cart_item_before_add_to_cart( $passed, $product_id, $quantity );
	$after = microtime( true );

	$_p_runtime = ( $after - $before );
	$second_func = $_p_runtime;
	echo "<br>End of 2nd function<br>";
	echo "\nTime frame: " . ( $_p_runtime );
	echo "<br><br>";
	############################
	
	if ( $first_func > $second_func ) {
		echo "First is higher by: " . ( $first_func - $second_func );
	}
    else if ( $second_func > $first_func ) {
		echo "Second is higher by: " . ( $second_func - $first_func );
	}
    else {
		echo "both the same";
	}

	exit;
}


// First method.
function pekky_1_remove_cart_item_before_add_to_cart( $passed, $product_id, $quantity ) {

	// Sample values: array( 23,45,43 );
	$stand_alone_products = array( 25221, 29237 ); //stand alone products
	$other_products       = array( 28745, 28746, 28747, 28748 ); // friendly products that can stay in the cart with others
	
	/**
	 *  Products attached to the standalone products
	 * These should be added to cart when a standalone product is in the cart.
	 *  patterns [{standalone_product_id} => array({force_sells_ids})]
	 */ 
	$force_sells_products = array(
		'29237' => array( 25556 ),
		'25221' => array( 29234, 29444 ),
	); //products attached to one of the stand alone products
    
	// Add only level 2 or level three program to the cart.
   if ( in_array( $product_id, $stand_alone_products ) ) {
		_pekky_sort_stand_alone_products( $product_id, $stand_alone_products, $force_sells_products );
	} 
	// Allow other products to be in cart together.
    else if ( in_array( $product_id, $other_products ) ) {
		// Make sure stand alone products aren't in the cart.
		foreach ( WC()->cart->get_cart() as $cart_item_key => $cart_item  ) {
			// Is the current product part of stand alone?
			if ( in_array( $cart_item['product_id'], $stand_alone_products ) ){
				// Yup, stand alone, remove from cart!
				// echo "<br>caughtttttttt<br>";
				_pekky_sort_stand_alone_products( $product_id, $stand_alone_products, $force_sells_products, false );
			}
		}
        WC()->cart->add_to_cart( $product_id );
	}
	return $passed;
}

// Works, different method, faster 😎
function pekky_2_remove_cart_item_before_add_to_cart( $passed, $product_id, $quantity ) {

	// Sample values: array( 23,45,43 );
	$stand_alone_products = array( 25221, 29237 ); //stand alone products
	$other_products       = array( 28745, 28746, 28747, 28748 ); // friendly products that can stay in the cart with others
	
	/**
	 *  Products attached to the standalone products
	 * These should be added to cart when a standalone product is in the cart.
	 *  patterns [{standalone_product_id} => array({force_sells_ids})]
	 */ 
	$force_sells_products = array(
		'29237' => array( 25556 ),
		'25221' => array( 29234, 29444 ),
	); //products attached to one of the stand alone products
    
	// Add only level 2 or level three program to the cart.
   if ( in_array( $product_id, $stand_alone_products ) ) {
	   // echo "<br>Standalone<br><br>";
		_pekky_sort_stand_alone_products( $product_id, $stand_alone_products, $force_sells_products );
	}
	// Allow other products to be in cart together.
    else if ( in_array( $product_id, $other_products ) ) {

		// Make sure stand alone products aren't in the cart.
		foreach ( $stand_alone_products as $p_id ) {
			// Is this standalone product in the cart?
   			if ( in_array( $p_id, array_column( WC()->cart->get_cart(), 'product_id' ) ) ) {
				// echo "<br>Otherrrrrr producccts<br><br>";
				// Product is there, remove.
				_pekky_sort_stand_alone_products( $p_id, $stand_alone_products, $force_sells_products, false );
			}
		}
        WC()->cart->add_to_cart( $product_id );
	}
	return $passed;
}

/**
 * Sorts the stand alone products
 * 
 * @param int $product_id
 * @oaram array $stand_alone_products
 * @param array $force_sells_products Products attached to the standalone products
 * These should be added to cart/removed when their standalone product is in the cart/removed.
 * Patterns [{standalone_product_id} => array({force_sells_ids})]
 * @param bool $add_to_cart (optional) true, add to cart, if false, removes, default is true.
 * @return bool false if empty field, true otherwise 
 */
function _pekky_sort_stand_alone_products( $product_id, $stand_alone_products, $force_sells_products, $add_to_cart = true ){
	if ( empty( $product_id ) || ( empty( $stand_alone_products ) || !is_array( $stand_alone_products ) )
	|| ( empty( $force_sells_products ) || !is_array( $force_sells_products ) ) ){
		return false;
	}
	//var_dump("yhhhhh<br><br>");
	$wc_cart = WC()->cart;
	$cart_func = 'remove_cart_item';
	if ( $add_to_cart ) {
		$cart_func = 'add_to_cart';
		// empty cart.
		$wc_cart->empty_cart();
	}
	$p_id = ( $add_to_cart ? $product_id : $wc_cart->generate_cart_id( $product_id ) );
	// var_dump("<br><br>".$cart_func);
	// var_dump("<br>product_id:".$product_id."<br>");
	// var_dump( "<br>function executed: ");
	$wc_cart->{"{$cart_func}"}( $p_id );
	// get list of standalone product id
	$product_force_sells_list = $force_sells_products[$product_id];
	//var_dump($product_force_sells_list);
	
	if( empty( $product_force_sells_list ) ){ 
		// wrong list
		return false;
	}

	// Also add the force_sells product to cart/remove
	foreach ( $product_force_sells_list as $_id ) {
		// var_dump("<br>Force_sales product id: " .$_id);
		$p_id = ( $add_to_cart ? $_id : $wc_cart->generate_cart_id( $_id ) );
		// var_dump("<br> function_exec:");
		$wc_cart->{"{$cart_func}"}( $p_id );
	}
	return true;
}