if you leave coca-cola on the car too long it will destroy the paint. I would not use it.
Give the clay bar a try. I took out a small light scuff on my car this weekend. My wife had water spots on here car a few months ago and claying took them out. We have hard well water. we normally go to the car wash to do the cars, but she decided to do it at home.....big mistake. it took 2 times claying the car to get all of them out. you will miss some of them the first time.