What works for a consequence to make an 8 year old eat dinner?

Don't have any other options for him. Get rid of all foods that are unhealthy and have only healthy choices. Reward him with "junk food" when he's had a few days of eating good foods. To really make a point, don't give him any sweets for his lunch or breakfast either. Non sweetened cereal and fruits and veggies for snacks at school. If he knows there's nothing else to eat in the house, he'll eventually get the hint.

for dinner, get rid of the side unhealthy options - ideally for everyone, but at least for him as for lunch and breakfast, there are plenty of fast and healthy options - kids get used to it. oatmeal, scrambled eggs and frozen bagels (use egg beaters, you just shake and pour), low sugar sugar and lowfat milk, fruit and yogurt and granola

Sometimes you can tweak foods to make them more appetizing. For example, my daughter doesn't like plain carrots, but she loves them when I cook them in orange juice. You could try, as the others said, just not giving him any other options than "healthy food or no food". My daughter went through a really picky phase, and at the same time a real "eyes bigger than her stomach" phase - she would load up her plate and then not eat any of it. So I let her choose how much food she wanted - figured she knew better than anyone how much she wanted - but I expected everything to be gone. If she couldn't finish it in one sitting, it would keep getting microwaved for the next meals and that's all she would be offered until it was all gone. Taught her to not waste food.

I have an eight year old daughter, same type of questions. I want to see what answers work.

If he wants to act like a baby then treat him like a baby. Don't serve him up ANY unhealthy options. If he doesn't want to eat, put it in the fridge and don't allow him to eat ANYTHING unless its his dinner that was placed in the fridge earlier. He will soon learn that not eating his dinner will result in him going to bed hungry.