Method 4: Fanning the door
Temperature change in first 10 minutes: 3.6 degrees/minute
I pulled out some physics for this one: I rolled down the passenger-side window, then "fanned" the driver's-side door about half a dozen times. The idea is to create a low-pressure area that literally sucks the hot air out of the car. When done, I started the car, pressed the obligatory "MAX A/C" button, rolled up the passenger-side window, and drove off. The car sat for a little longer on this day, and the temperature spiked to 135 degrees, which would've been a good start if my goal was a nice long sweat in a sauna.
After five minutes, it was only down to 124... and then came a much bigger difference than I anticipated. Just one minute later, it was 116, followed by 107 after another 60 seconds. By the 10-minute marker, the temperature was already below 100, at which point I switched off dear old "MAX A/C." Five minutes later, the ambient temperature was down to 91 degrees. It didn't stop getting cooler and cooler, though, and by the time 20 minutes rolled around, it was a downright comfortable 86 degrees. Outside, it was the same 100-degree day as the previous two.