I normally wasn't allowed to eat any sweets, including soda, as a child. However, on a special occasion, such as Halloween, another child's party, etc., I could eat whatever I wanted.
My point being that, as long as the child doesn't have a medical reason to not be allowed sweets (diabetic, ADHD, etc.), I think overloading on sweets a few times a year is fine, as long as his sweets are restricted the rest of the year. I think it's also good for the child to learn that sweets are special occasion food, not everyday food.
I think it's a lot healthier for a child to eat a whole bag of chocolate one day a year than to drink soda with his meals or have dessert after each meal 365 days a year.