Rehab Protean is a truly unique offering, and as such it's really difficult to assess its quality, since it seems like it could be different things to different people. The nutritional profile makes it clear that Monster was trying to combine a protein shake with an energy drink, but I'm not sure how necessary this product really is, as the idea of heavy caffeine plus protein was enough to make my stomach turn. However, I decided I had to try it. The result is a strong "meh," as this provides less of what Monster does best along with less protein than you'd get in the average shake. While Rehab Protean does offer 170 mg of caffeine per can, it comes along with 15 grams of protein, which blunts the energizing effect. This is a pretty low-carb offering, with 10 grams in the entire can (8 grams of sugar), and offers other fairly standard Monster fare such as B vitamins, taurine, tea extracts, carnitine, quercetin. This doesn't really feel like a high-performance beverage, although it does provide energy. They don't seem particularly suited for athletics other than the protein, and one scoop of protein powder plus a caffeine pill or coffee would be cheaper. The taste is bland, like an overly watered down protein shake mixed with low-carb Monster (which may be the case), and the result is not unpleasant but also not enjoyable.