I offer an appetizer rather than making the low-blood-sugar child wait for the meal. Apples w/ peanut butter while I'm making lunch, frozen blueberries if it's before breakfast, etc.
I try hard to honor their hunger/fullness cues so I don't want to force them to eat if not interested. I'm also not going to hand out a cookie right before dinner, but if they want to have apple slices, a peach, etc while I cook I'm totally fine with that.