Yup, and that's not about sugar, the real problem is H3PO4 acid, which is in every cola drink...

i think coca cola zero is worse than ordinary coca cola light, which makes it pretty bad

Since where I live we have one of the best quality coca-cola in the world (said by the official coca-cola site some time ago, something to do with the quality of the water) I have no reason to buy coca-cola zero/light/diet. Just the good old fashion Coca-Cola.