As far as I know most kidney stones are caused by too much tea or salt or not drinking enough water. Some people will get them more due to genetics too.
Coca Cola I haven't heard before with kidney stones, but I wouldn't be surprised, it is certainly not good for you. I think your teeth would be affected before you get kidney stones first!
I think a fair comment is to make sure you drink lots of water. A big glass before bed I have found makes you feel a lot more healthy in general. It makes you get up for first prayers too!!!