I have found that in children who have had lots of sweet things including store bought juice, they will not drink much water, so I think it is really something that you have to work with from the beginning, and not ever give them much sweet stuff. I always make sure to offer DD water even if she is not asking for it because most of the time she will drink it. I also sometimes squeeze some fresh lemon into it and she loves that.
Be careful only to buy good high quality green tea, because the cheap Lipton stuff is made from old green tea leaves that have high levels of flouride in them, which can be toxic if you drink too much of it. The quality stuff is made of young leaves that have low levels.