Lost the keys to my gas cap need help!! lol

[Coronadj]

So I am working on my 69 c10 short bed project and one day I left my keys to it out in the open and my baby brother grab them and now i can't find them. but lucky I left the truck unlock so I was just gonna take on the door lock and take it to a shop that make a key so i can lock it and turn it on. but now I don't have the to the gas cap so whats the best way on taking off a gas cap with out anything going in the gas tank?