Inexpensive short-term cooling solutions?

I'm trying to make the jump from hobbyist to earning some extra income off my woodworking. I'm working out of a two-car garage roughly 20x20. I need to double check (currently sidelined by COVID), but at least two walls are insulated, most of the third, and there's a small attic space above the garage that has insulation in it.

I'm in a heat dome right now, so the garage is topping out at about 100 degrees during the day.

I know from looking at other posts on the topic that I need finish out the insulation before bothering with a minisplit or other conditioning hardware, but I don't even have the money to invest in AC at the moment anyway. I need the side hustle to turn a profit before I drop that kind of money.

Currently, I just open the garage door and the back door and run a fan to get as much air flow going as possible. When it's not 90 plus degrees out and humidity over 70%, I can tolerate it. But I live in Missouri and the humidity isn't going anywhere.

Does anyone know any cheap hacks for cooling down a space? At this point, I'm considering filling a 17 gallon storage tub with a block of ice and water and putting it behind the fan.