$site_args = array(
       'network_id' => $wpdb->siteid,
       'public'     => null,
       'archived'   => null,
       'mature'     => null,
       'spam'       => null,
       'deleted'    => null,
       'limit'      => 1000,
       'offset'     => 0
   );
   $siteList = wp_get_sites($site_args);

   foreach($siteList as $site){
        switch_to_blog( $site['blog_id'] );

        $locations = get_nav_menu_locations();
        $menu = wp_get_nav_menu_items('main-menu');

        foreach($menu as $item){
            if($item->post_name == 'resources'){
                $resources_ID = $item->ID;
                 $tips = wp_update_nav_menu_item($locations['main-menu'], 0, array(
                    'menu-item-title' =>  __('Marketing Tips'),
                    'menu-item-classes' => 'tips',
                    'menu-item-url' => '/resources/tips/',
                    'menu-item-status' => 'publish',
                    'menu-item-parent-id' => $resources_ID
                 ));
            }
        }

        restore_current_blog();
   }