What is a frugal and healthy-ish fizzy drink?

I love carbonated beverages, especially at work. They just feel nice when I drink them. However, I was doing mountain dew kickstarts for a while and they just make me feel so awful when I drink them. Today I had a Glaceau fruit water, and that had the same amount of fizz and I feel fine. Just wondering if anyone out there knows of the cheapest yet still actually fizzy drink out there!