i would suggest trying kombucha. don't know what area you live in, but it is getting more and more mainstream. it is super healthy-- no sugar or sweeteners-- and it is not carbonated, but fermented, which makes it fizzy. it's full of good bacteria for your gut as well as b vitamins. i haven't had soda pop in ages, but i do crave something "carbonated" and kombucha fits the bill. a great brand is g.t.'s kombucha. you can also grow/make your own, if you are so inclined! i do and i love experimenting with different flavors. you can purchase starter sets online and it is as easy to make as brewing tea.
good luck!