I brought snacks last Saturday for my 8 yr. old boy's soccer game. I took Rice Krispie treats, which are light and somewhat healthy snack and juice boxes...maybe you could dress the Rice Krispies up with halloween colored m&ms or something on top.
Candied apples are Halloween/fall treat - but they could get messy as ppl are eating them on the way to their cars. Maybe sliced apples(healthy) and the little mini-caramel dips (again hard to eat as walking to a car or getting in a car).
If you're not wanting as healthy and this is their last game - you could get a small cookie cake at the grocery store with some kind of Halloween picture on it. We've done this before for my 10 yr old's b-day that landed on a soccer game day - we brought a cookie cake and the kids loved it after the game! Ofcourse don't forget napkins and a plastic knife to cut and serve the pieces of cookie!
Good Luck!
~H.
Mom to 3kids-10 yr. old (girl),8 yr. old(boy),2.5 yr. old (boy)