Regular milk is not good for little kittens. Do you have a pet store nearby? KMR (kitten replacement milk) is available there and you can feed him that. Warm it up a little as you would a human baby.

If he's older, you could try a little baby food (nothing with onions since they are poisonous to cats) and warm that up for him.

Do you have a dropper? Try sucking the stuff up into a dropper and squirting it into his mouth. Sometimes they don't want something until they realize it tastes yummy. Of course, being late at night makes it oh so easy to get all this stuff!