¿Cuál es la diferencia entre He went in for candy just after he tasted a candy. y He went in for candies just after he tasted a candy. y He went in for the candy just after he tasted a candy. ?Puedes dar oraciones como ejemplo.

hmm grammatically the third one is the closest to being correct
>> "He went in for the candy just after he tasted IT (or "the candy" not "a candy)

also context wise, we would never use these sentences because it just does not make sense.
Someone would not go in for a candy but "choose"
also my answer differs depending on what the context or story is which is why im hoping that you can tell me what it is about

because if the candy was on the floor and everyone is running to get the candy you would say...
" I dived onto the floor to get the candy before anyone else"
but we wouldn't say "went in"

OR if you meant "went in the store?"

do you see what I mean? there are sooo many interpretations judging by your sentence because we really don't say it like that.

Hope this helped:)