I tried to pry out the snap rivet in the hinged gas cap cover, I got it to move a bit and when I pushed it back in I heard it snap back into position. I think that would work but I did not have the nerve to force it out further. My rivet was a one piece design, not two pieces as in the photo in post number
A neighbour of mine tried to pump out the gas that his wife had put in their diesel-powered VW, he was using a pump powered by an electric drill. They had two VWs, a gas and a diesel-powered one.
He did achieve to get all the gas and diesel out but not without disastrous consequences. So do not use anything that sparks or has a heating element that exceeds the flashpoint of gasoline.
I gave him the pics, I told him that one day it would seem funny, this was ten years ago and I often wonder if he has seen the funny side of the episode yet, he is still married so at least that's something. He had to repave the driveway though, asphalt really cannot stand that heat.