"treats" or "rewards"

My question is about using food as a “treat” or “reward” . The specific example is that when I’ve had a rough day – emotionally or physically, I decide that I can go off my “no sodas” as a reward or treat – for my “hard work” in handling the day basically. One soda, with a refill of course, is enough to satisfy my thought of “getting” a reward (or treat). It doesn’t happen often, maybe once every two weeks.
I’m dancing all around the advice about going off protocol, exceptions, coming up with a model, etc., but I’m not sure exactly where to put this. My thought is that it is not healthy to have any type of food reward system but I’m wondering what your thoughts are about this. Is this just something that would be considered an exception? Thanks for all you do!