How cool is this bottle? Looks like they took a hint from Metromint.
First of all, this isn't carbonated, which makes it taste sort of like a cheap flat fruit-flavored soda. The taste is sour and unremarkable; I'm not sure what açai berries taste like, but I hope they don't taste as artificial as this. The closest thing I can compare it to are blue Sweet-tart candies. And the flavor lingers in your mouth for a while, which may not be such a good thing--But it would make a great mixer with vodka. Hydrive is billed an energy drink (even comes with its own caffeine warning: "Not recommended for children, pregnant women or people sensitive to caffeine"), and as such, it ain't that bad. Better than Monster, anyways. And it's made with spring water, has only 25 calories and no high-fructose corn syrup, if you care about shit like that.
Caffeine-wise, Hydrive supposedly has 38% more caffeine than the "leading energy brand." Assuming they mean Red Bull, that gives Hydrive around 110.5mg of caffeine: The equivalent of two Mountain Dews. Incidentally, I'm one of those "people sensitive to caffeine" the label warns about, so I'm feeling uncomfortably jittery right now, but I expect that most people won't get this effect.
All in all, this isn't bad, but I'll stick to Sobe Adrenaline Rush.
Verdict: ***/***** (so-so.)