Food truck? I hired one for my wedding and it was only ~$18/person. That includes a dessert. But we were paying for people.

Just let people buy their own food from the truck. I think they only have a $100 travel fee. Obviously this depends on the food truck you order, but we didn’t have a hard time finding a reasonable one. They also have drinks as an option most of the time.

For providing your own drinks, do you have any close friends involved in this event? Maybe you could ask them to scrounge together some money. Because - like you said - even water is going to be expensive for 100 people.

If you don’t have anyone that can help pay, you’re super limited. Gatorade sells small 12oz versions of their drinks in 24 packs. It was like $10 at the store. So $50 for Gatorade options for 100 people. Water is probably comparable. They also have 10oz waters in 24packs. Those are cheap. Soda and solo cups can actually cut down on cost since you can buy soda in 2liter bottles.

Now that I think about it, those large coolers (like the orange ones you see on Football fields) only cost $30-$50. Buy two of those and just fill them with water. You can dump ice in them. Then provide people with cups.

If you want to be really cheap, Walmart has a pretty robust return policy. You might be able to return those to Walmart after you use them. Not ethical, but cheap.

You can also just scout Goodwill and other thrift stores. You’d be surprised what you can find. You basically need any large coolers/vessels for water.