I have a suggestion about the sucking.

1.) Don't use your mouth. Even if you don't actually get liquid gas in there, the fumes aren't good for you. You probably knew that already.

2.) Get a turkey baster with a big bulb. Bend your siphon tube such that you can suck on the end of the tube and not actually draw anything - the bulb on the baster stays compressed. Unbend the hose and let the baster bulb expand. Bend the hose again, and squeeze air out of the bulb without unbending the siphon tube.

3.) Repeat 2.) until the gasoline gets close to the end. As soon as the level of the fluid is lower than the bottom of the tank, gravity will do the rest.

In my youth, I often liberated gas from my parents' vehicles in this manner. I don't think I paid for gasoline throughout all of high school.