Amazon has the Dental Fresh Advanced Whitening Water Additive Dog Breath Freshener (8 oz) for $7.34 - 10% off (check “Save an extra” box, eligible on first S&S order for this product) - 5% off with Subscribe & Save (can cancel anytime) = $5.39 with free shipping on $35+ or with Prime (extra 10% off for 5+ subscribe and save orders).

Add 1 tsp to every 8oz of drinking water.