Well....its I guess technically still water but...
Water flavoroed with Basil or mint (yes try it, yum)
Do a lot of lemon or lime in water
sometimes I just have to have some bubbles so soda water with any of the above.
Unsweetened iced teas. There are many herbal ones that make excellent iced teas like peppermint, lavender, rose hip, hibiscus, huckleberry, raspberry leaf all with no caffiene. If your not into any of those why not make your own decaf iced tea/unsweetened? In fact with colder weather coming I will suggest others great steeped in hot water to make a "tea" for hot drinks. Fennel seed, cinnamon sticks, sage, mint again
... all in your spice cabinet already!
I dont drink soda (discovered years ago how much it made me feel like S*^T) I have one once in a great while but then the sugar makes my mouth feel nasty (can you say furry teeth?) and thirstier...go figure.