Make a CPT post sticky anytime it's updated

sticky-cpt.php

<?php
add_action( 'save_post', 'child_sticky_factory', 99 );
/**
 * Allow sticky posts in a CPT
 */
function child_sticky_factory() {

	$post_id = get_the_ID();
	$stickem = get_post_meta( $post_id, '_child_sticky', true );

	if ( 'some_post_type' != get_post_type( $post_id ) ) {
		return;
	}

	isset( $stickem ) ? stick_post( array( $post_id ) ) : unstick_post( $post_id );

}