I think that you're probably on to something here, and it's probably related to your alcohol habits. Alcohol is a really common means of medicating anxiety and it's also just a habit-forming thing in and of itself. The problem is that sodas don't even have the immediate anxiety-reducing effect that alcohol has. The sugar and (probably) the caffeine are going to increase that sensation of anxiety, and they're also going to increase your anxiety in general, thus making you crave more soda.
To be frank, one jack and coke is undoubtedly LESS unhealthy than six diet sodas.
As a practical note of advice, I suggest drinking club sodas when you get that craving. Really concentrate on reducing that dependence on the sugar, or the flavor, or what have you. It'll be good for you as a fighter and good for you as a person. Good luck.