Children won't eat dinner

[PinkFluffyBubbles]

My 3yr old and 18 month old sons won't eat their homemade dinner for 2 days consecutively.
Today they have eaten cereal for breakfast and a sandwich and banana for lunch. No snacking or sugary foods in between.
When given dinner they have one spoonful then refuse to eat. I can't afford to make them something else. But now they're Hungry and in bad form. Yesterday was the same and the 3yr old was awake in the night asking for a bottle of milk, which he stopped taking a year ago.
Do I give in to whatever they're asking for?
Or stick to dealing with bad tempered hungry children that wake during the night?
Please advise

What food are you offering?
Maybe offer a slice of toast before bed

I don't give in, if they don't eat, that is it. I do still offer fruit for afterwards though.

Mine don't wake in the night though, thank god! That would likely change how I dealt with it. 🤣. Maybe a banana before bed?