I am a Diet Coke-aholic (who's currently going through withdrawals trying to cut back to one soda per day). I find at Disney, I drink a LOT less soda. Depending on the time of year you are going, you are going to need to drink good old fashioned water to stay hydrated. If you hate water, bring Crystal light (or similar) packets to flavor the water. But if you are going in September...which I think you are...plan on drinking a lot of water in addition to soda.