If you are in a city setting with lots of foot traffic – I would highly recommend selling cellular recharge cards (cricket, verizon, tmobile, etc). I have countless people each day ask where the local cell store is – where they can get top-up cards.
AZ that would be a great idea but you also need a machine with a phone line to swipe those cards to activate them (similar to a store gift card). I once read where a hot dog vendor sold sunscreen which isn’t a bad idea over here in the southwest. DD