My 4 went hungry if they did not like what was offered to them, no treats or snacks several hours prior to meal time, was the rule. Also avoid sugary drinks and juice, they are quite clever at that age and can be quite vocal if they dont get what they want.
One trick I did learn was to dress the food up, make a face with peas and mash, write their name on the egg when boiling them etc.
Their favorite food one day could be the food they hate the next.