My dc are allowed treats most days, so for example my ds will get a small chocolate bar with his packed lunch and then a biscuit after school.
But that is it. Any other snack or pudding is fruit, chopped veg, oatcakes that kind of thing. I might be more relaxed on birthdays or holidays.
But I seem more strict about it than others and I don't want my kids to have issues. I try to have the philosophy that treats are fine in moderation.