In the long term it isn't likely to affect you. In the short term it may cause water retention. I did this with diet soda weeks ago. I hadn't been taking it, and then had a couple of cans for a couple of days. Suddenly I was retaining water like mad. Three or four days after that it was back to normal.
Other people react even more strangely to a day of junk food. They lose weight, and it becomes an issue. I've seen some think that this means they can do it more than once. If your body reacts that way, please don't fall into that trap.