Probiotic Kefir
I think you can make kefir from milk or water, right? I imagine the milk one would be a good source of protein. It's sorta like yogurt, but drinkable. What's it say on the label?
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I absolutely love it and it does satisfy me for one of my six meals. I found a plain flavored one (Lifeway) in my area that only has 12 g of sugar, much closer in sugar to regular milk. The other great thing is that I can easily take it with me. It's thick when you pour it right out of the fridge (my favorite), but if it sits out for a while it gets thinner.