What's wrong with water? Cool, clean, filtered water?
If you really feel it needs something , squeeze a bit of lemon and lime (no sugar) and drop in some ice cubes. It's refreshing, it's delicious, it's healthy.
If you are hooked on bubbles then buy plain soda water and add your own fruity goodness with NO sugar.
Man was not designed to live on soda drinks. I am directly involved via my employment in the mixing and bottling process for the worlds largest soda company. These drinks are great and the quality of the product is extremely high, but constantly replacing water needs with those type of products has side effects.
If you are drinking something that don't taste like nature, man has probably screwed with it and this doesn't make it better for you.