Wet cat food (not the chunks kind) works well.
If he doesn't want to take it in that even, if you grab his mouth from behind his head where his largest tooth is at on the side (third premolar) you should be able to tip his head back, then use your other hand to open his mouth and plop the glob of "cat food a la pill" into the back if his throat. You usually don't have to worry about choking unless you shove it WAYY back in there.