...- feed the cast and crew. If you're not paying them and particularly if you're asking them to schlep a distance to participate, you need to do that much. IMAO. And there's a selfish aspect to it - bringing meals in keeps the production running on something resembling a "schedule" (hah!).
Also, one rule I learned: never ask the crew to give you orders for meals. If you do, what ends up happening is everyone tailors their order to a degree that it wastes a lot of time getting lunch ordered and sorted out. I usually cater with a variety of sandwiches and snacks so that there's something everyone can eat. It saves time and cost. It's good to know beforehand about anyone's requirements (dietary or otherwise) and have pre-picked food that will cover these.