If allergies or simply an aversion to animal products means that cow's or animal milk isn't your thing, then a soy beverage (a.k.a. soy milk) is a good alternative. While soy protein may not be as effective for muscle recovery as milk protein, the comparable seven grams of protein per cup is a still a significant amount, so consider adding soy into your rotation. But keep an eye on the sugar content, as the amount can vary widely by brand flavor. Some brands pack up to 160 calories per cup, due to the added sugars.