I don't have AC but my apartment lease covers unlimited water usage and the water is very cold. How can I best use this to cool my home?
I've searched around and mostly seen people create custom radiator builds attached to their water supply, but that's beyond my skill level and I'm not sure if linking it directly to the water supply via piping would violate the lease or not. Are there any solutions a bit more DIY that I could take advantage of?
I don't know how big your apartment is but why not a window unit. It's probably the most efficient way to cook your apartment down short of redesigning the building.
It's either that or maintain a swamp cooler that won't work on humid days and can cause respiratory infection if not cleaned properly. A renters options are very limited and a window unit is a pretty good compromise if you don't want to loose a deposit.
If you want to sit in a sweltering room during a 100° day, no one is stopping you. I've heard it's a pretty typical thing for Europeans anyway. I'm not judging, the guy wants to cool the room down.
OP would probably be better suited with a portable AC. Most apartments I know of ban window units because they can fall and hit people if not installed properly.
When getting a portable AC, get one with two hoses as they're much more efficient since they aren't blowing cooled air outside (and sucking hot air in from every gap in the exterior walls.