I guess it could be a water sprayer. I removed the inline humidifier so I could blow cold air directly I into my garage. There is nothing I hate more than working in a hot garage.
I did mine last year. My a/c and heater ducting runs directly above my garage, so I punched a couple holes and added two vents. Now I have a/c and heat in my garage all year. I just close them off when I'm not going to be out there. It's something I should have done 10 years ago when I moved in. It works extremely well, and I've never seen a change in utility cost. If anything it's lower now.
I just open the door into my house and set a fan in the doorway. Then I have a 80"x36" vent.
But I've often thought it would be nice to have a AC/heat unit out of a hotel room or something.
Update...now that it has gotten really hot and humid here (90-95 degrees, 50-60% humidity), the HVAC unit can't quite keep up with the garage and the rest of the house. I miss winter
I need to get one of those portable AC units from Costco. The FL heat sucks in the garage...on the plus side, I lose about 10lbs...better than a sauna. I had to spread my clay/polish/sealer/wax detail over two weekends. I'll tackle the interior and engine bay this weekend.