Depends on why he is refusing dinner TBH. Is he refusing as he is just not hungry?? If so, then when mine were tiny they just had a bottle of milk, or a yoghurt, and then went through until morning.
If he is refusing due to the meal being too big (and they can be overwhelmed by the size of portions, especially if they have eaten well in the day), then maybe start just offering smaller portions, or go with snack type food of crackers, cubes of cheese, chopped fruit and slices of ham.
Contrary to popular belief, children don;t NEED a hot meal every day. It took me until DC5 to figure that one out, and many mealtime stresses....
I often just offered mine something on toast, or pitta pockets.
Don;t ever make meals a battle.....it just sets up everyone for years of food issues, and believe me, that is hell on everyone .
Oh, and cereal isn;t the food of the devil BTW. Nor is sugar. Everything in moderation is the key.
You deny a child any sugar, then by the time they go to their first party without you, they are likely to put their head into a bowl of skittles and inhale, and then you get back a whirling dervish in place of the sweet child you dropped off ...