select sub sites in the network

// WP_Site_Query arguments
$args = array(
	'site__not_in'      => array( '1' ),
	'fields'            => 'ids',
);

// The Site Query
$site_query = new WP_Site_Query( $args );

// The Loop
if ( $site_query ) {
	foreach ( $site_query as $site ) {
		// do something
	}
}