Old camping technique.
We learned to make them in the Boy Scouts out of orange crates and burlap bags.
They work on the same principle as the "swamp cooler" type air conditioners.
Keep the burlap wet and the evaporation keeps the contents cool.
Something like this:
Just Google "evaoporative cooler" to get some ideas.
**** “We learned to make them in the Boy Scouts out of orange crates and burlap bags” ****
Finding Burlap these days is tough!