It the caffeine.  Caffeine is a very addictive drug, more people are addicted to it then cigarettes. Yeah, most people don't understand just how highly addictive caffeine really is, that stuff is no joke. Coca-Cola originally began using caffeine as a replacement for cocaine...that should tell you something about how addictive it is.    I know what you mean leondegrance, I'm a Coke head too:D I usually drink 2 or 3 of those suckers a day, it can be a difficult habit to break.