There is almost nothing* like sugar drinks in the natural world our bodies evolved in. Sugar drinks are about as different as tea leaves and pure cocaine. It's is no coincidence that both are refined white powders. *honey
On the other hand, grape juice, while not 100% natural, I’m not sure how it fares against cola (just considering sugar, not the rest of the junk)
Once I drunk some not-still-done wine, basically grape juice where the fermentation started, and so some bubbles were present. That was the most natural and delicious soda I’ve ever tasted… I do bot even hope it can be healthy to the body… but my soul ;)