Whatever they want" is a huge range of possibilities. Some "bad" foods are worse than others.
But, it is your health. Diabetes, especially type 2, is a progressive disease that can change over time. Right now, you are controlling your levels with just metformin, diet, and exercise. But, failing to maintain consistency with that diet can speed up the progression of diabetes to the point that metformin would no longer be enough with diet and exercise and you would need more medications. As you need more, the price of that medication also goes up. The risks of complications also goes up.
Basically, binge eating on whatever you want on every weekend will have a price and only time would let you know exactly what that price would be.