Supper's a battlefield

My son has a wonderful disposition. He is sweet, kind and polite. Except at mealtime. Good God, the child turns into el diablo. He demands things, throws food, throws his milk cup. I get pissed and yell. He gives me an evil smirk and keeps doing it. I wind up feeling like I'm going to cry and totally manipulated (which is the whole point, dontchaknow).

We've tried time outs. Then he just asks for them, which defeats the purpose. Tonight, we started not giving him back his food or drink. I'm not really sure how that's going to work, because the whining for milk really gets to me. If anyone has any suggestions, I'm all ears.