It's best when mixed with "other" beverages, if you know what I mean.
Edit: Monster is alright but I've always liked Amp from Mountain Dew way more. This is coming from a caffeine addict. If I don't get caffeine by noon, I get a horrible migraine. Chemical addictions, FTL. Either way, the best thing I've ever done to get energy is buy one of those 80-hour sprays. Ten sprays under the tongue and hold it there for about 45 seconds, then swallow. Oh, it tastes like hell but you'll get hyper. Real hyper. As far as taste goes, Amp is my favorite. Not a lot of caffeine compared to Monster(Which has the most caffeine in it, aside from Cocaine) but still tastes pretty dern good.