I gave up soda nearly a year ago and haven't looked back. I don't like beer to begin with.
For me it's water or mint tea. I usually have some loose leaf mint herbal tea around, and I'll steep it hot before sticking it in the fridge to cool down, then drink it iced. Personally mint has always been a "cool" flavor to me, so it's really nice to have iced.
Crystal Light is also good, and living with my sister we can make a gallon of it and it will last for a while, which is always nice.
If it wasn't so expensive, I'd buy fruit juice all the time and have that, but I'm picky and can only really stand the good stuff. Oh well, it's always nice for a treat.