Waterpik Flossing Toothbrush – Costco Sale! by Rhonda October 26, 2021 October 26, 2021 *UPDATE* 10/25/21. With the Waterpik Sonic-Fusion 2.0 Flossing Toothbrush from Costco, you can brush and floss at the same time! It’s up to 2x as effective as traditional brushing and… 0 FacebookTwitterPinterestEmail