Amazon has the 12-Pack of Gatorade Zero With Protein, 3 Flavor Variety Pack (16.9oz bottles) for $12 - 5% off with Subscribe & Save (can cancel anytime) = $11 with free shipping on $25+ or with Prime (extra 15% off for 5+ S&S orders).

Contains zero sugar, under 60 calories and 10g whey protein isolate. Includes Cool Blue, Glacier Cherry and Fruit Punch flavors.