When are they expecting the extra meal?
It is hard as some families literally let their kids snack all day. So their stomachs are trained to need to eat constantly. Does this child eat a substantial amount at the 3 meals offered, or just graze?

When I had my group of 5 toddlers I did do an extra morning snack as they did the 2 naps, then they switched to one early nap (at 11:30) and it left big meal time gaps.

But, for a 7.5 hrs day I don't think a child should NEED 4 meals...they need to be trained to eat more when it is time to eat.

Can the parent provide a quick snack before or after coming? Do they feel the child is losing it when they get home and feel more food would solve this? What is making them request more food?

I do part time care right now and I have a 1 and 2 yr old that only come 2-2.5 hrs in the afternoon. They eat frequently at home. I feed a snack shortly after they come and I know they are legitimately hungry by the end of their time here...but I can't be feeding them 2x in 2hrs. Not only does it take up time but it costs money. AND I know they are walking home and eating immediately after being picked up, so they just need to adapt and will eventually eat more when I offer it and their bodies will adapt to waiting till supper.

My main concern with kids that snack all day is it is generally not the healthy foods they fill up on and then they are not hungry enough to want to eat the main meal foods (healthier choices). The NEED to be hungry when they come to the table. Maybe explain this to the parents?