I think as adults we all have days when we just don't fancy what's for dinner, don't eat much of it and then, if we're hungry later, grab a snack. It is only a big issue if you make it a big issue.
Children do not need adult policing what they put in their mouths. Put the food out, let them choose how much they take/eat, let the get down when they have had enough.
If, once in a blue moon that means they need a bit of fruit/toast/milk before bed that's fine.
The more you try to be in control, the more likely you are to kick off a battle of wills that you will never, ever win.
If you let your child regulate his own food intake and listen to his own appetite, he is much more likely to grow up with a long-term healthy relationship with food.
If a child is 'acting up' for attention by refusing food, the best response is to refuse to engage. You've been doing the right thing by refusing to have a battle. Keep doing it.