Putting a hole in a gas tank?

I have a 1990 mazda 626 and im trying to get rid of it. the most i can get is at the scrap metal place and they will pay $323 to crush it. the only thing is they wont take it unless the gas tank has either a hole in it or the gas tank is removed. And you cant siphon it out b/c they said they need to be able to SEE that it doesnt have any gas. Putting a hole in it would probably be easier for me since i dont know much about cars. but i dont know if it's dangerous or not. i heard that any spark cld make it ignite. my friend said to use a hammer and a screw driver but idk.