I try to drink at least a quart of water daily, and my doctor suggests that more can be helpful. Unfortunately, I don't care much for plain water, and to help increase my intake, flavor is added to the liquid. Usually, I make a slow-steeped tea and drink it from the fridge or at room temperature. Less frequently, a bit of fresh lemon juice is added to a bottle of water. I also drink sugar-free flavored mineral water, such as Trader Joe's.
Additional ideas for adding sugar-free flavor to water would be great. I'd like to stay away from the various "unsweetened" drinks that fill the market shelves ... TJ's mineral water (and another similar, local brand) is as far as I'll go in that direction.