Is how much candy correct grammar?

Here's why:

* "How much" is used to ask about quantity of uncountable nouns. Candy, as a general term, is considered uncountable.

* "How many" is used for countable nouns. You would say "How many candies?" if you were asking about the number of individual candies.

Example:

* Correct: "How much candy did you eat?"

* Correct: "How many candies did you eat?"