sunrise.php

<?php

/**
 * Force cookie constants to be local domain / path
 * after multisite is loaded.
 */
add_action(
	'ms_loaded', function () {
		$site = get_site();

		define( 'COOKIE_DOMAIN', $site->domain );
		define( 'COOKIE_PATH', $site->path );
		define( 'SITECOOKIEPATH', $site->path );
		define( 'COOKIEHASH', md5( $site->domain . $site->path ) );

	}
);