I found this tasty concotion at my local GNC. It's a "supplement drink," with 40g of protein in the 16-oz bottle! I know of two flavors, Grape and TropiCURL Breeze. I've tasted the latter, and it was better than I expected. Not grainy at all, rather like a fruit drink. A serving contains 1g of carbs, and it's sweetened with sucralose (Splenda) and ace-K.

Pricey at $3 a bottle, but if you need a quick fix it's worthwhile.