The problem I see with this is that if, for whatever reason, you do happen to drink that soda one day, your pretense that you are "the sort of person who does not drink soda" is totally blown to pieces and you cannot continue to follow your system because you are no longer capable of deceiving yourself.

Only if you choose to make that response to a lapse part of your system. But why would you do that? A soda is just a soda. All else is the meaning you attach to it.