I have at least one 16-oz. bottle of green tea per day (though home-brewed would be best, because it would have no added sweeteners). I think it gives me a bit of "mild" energy (not hyper, like coffee might). I think the benefits of green tea aren't necessarily that overt, because it works as an antioxident to protect your cells. In the long run, it might help prevent some illnesses (but you'd never know, because you can't prove that something "would have happened" if you hadn't done X).
FYI (if you didn't know): when brewing green tea, do NOT use boiling water, but water that is below the boiling point (either before it boils, or left to cool a bit before pouring it over the tea bag). Don't steep for over 3 minutes (some say 4, but some say 2, so I'll take the middle ground). Agitating (dunkig) the teabag while it steeps releases up to 5x as many antioxidants, but covering the cup while it steeps retains more of the vital properties that otherwise can go "up in smoke" so to speak.