I always carry a bit of a snack with me. I use a ziplock bag with a sausage & cheese packet (had a guy offer me $5 for it once hehe), cheese & crackers, granola/breakfast bar, some chocolate squares or an envelope of cookies.

If I'm on a longer flight, I use my BuiltNY lunch bag to keep my bottle of water or pop cold and the meal either warm/cold (usually a subway or other sandwich).

The "100 calorie" packs are great sizes for this & also the checkout displays at the grocery store/gas station are great places to find things in individual packs.