Monday:
4 year old: "I don't like pizza"
me: "I do. Eat or go wash up."
Kid goes to wash up.
4 year old, later: "I'm hungry."
me: "Go play toys."
Tuesday:
4 year old: "I don't like chicken."
me: "I do. Eat or go wash up."
Kid eats.
It becomes a non-issue when the kid realizes you don't care if they eat or not.
If parents ask why their kid is hungry I tell them to ask their kid. Natural consequences.
Obviously, I plan my menus based on the groups' true dislikes, not just mood swings. There is no arguing a true dislike. I don't force kids to eat anything and I make substitutions on days I know a kid won't eat a specific thing. Ex: I currently offer baked sweet potato slices on cooked carrot days and sweet peas on string bean days. It is not a lot of effort and both kids eat very well with everything else.