WOW! 3 liters a day?! I have never been a soda addict, but from what I have heard it sounds as addictive as tobacco. Good luck! I'm guessing you don't like diet Pepsi. Is it the sugar you miss, or the caffeine?
I used to drink 3-4 cups of coffee a day. About a month ago I switched to decaffeinated green tea. To be honest I can't tell any difference, nor did I go through any type of withdrawal. I'm sure there are some internal benefits going on, I just can't feel them.