What's the most efficient way to keep these guys cool during

>>2413052
Long lasting ice packs placed onto a dinner plate to catch drips and save bedding, make sure it's non toxic or just wrap it up in something like a towel if he chews.

Fan blowing across the corner of the cage through a platform, never directly into the cage.

A frozen gallon of water on a deeper plate will last all day and provide clean ass water by condensating.

This is pretty easy stuff to solve. Ice water is everyone's go to, but if your teeth suck it hurts like hell to drink, so don't do it if you don't want him to develop sensitivities.
And yes, you are about to have a dead animal if you keep that up. Frozen gallon of water would cool a whole 4 cubic feet if isolated, build a little cube area with this inside so he can enter and exit. You have to let them do it themselves because your choice about their room temperature will always fail.