Any personal cooling gadgets that actually work?

Would love to stay inside but I have to be outside some and driving from place to place and leaving my car parked. Obviously thousands of cooling options but which ones really work?

Was going to order a Mission towel supposedly they stay cold for a few hours when you wet them, never tried one.
Never owned a personal mister.. they look cheap as hell but I guess they are like $5 so maybe you expect it to break and get another one.

Was thinking of getting a sheet and just throwing over my car front window and side windows, maybe roll it up in the window to keep in place. Is this crazy? Would it work better than those reflective sunshades you stick under your mirror?

Any other gadgets out there that work well?