Well, truth be told they are both kind of awful. It's said that you can clean corrosion off of a cars battery terminals with Coke so what's that tell you. Personally I prefer diet green tea. Turkey Hill, a local mini mart chain, also produces many high quality food items, one of which is their own version of green tea. It's refreshing qualities are almost addictive and I practically live on the stuff. Otherwise it's hard to beat some plain old spring water.
Now if your looking for something alcoholic that's a whole other story. But I'll leave that topic for someone else for now.
P. S. I am not in any way affiliated with the big evil Turkey Hill corporation, I just like giving credit where credit is due.