tl;dw:
Modern cars are not as easy to siphon gas out of. You’re going to need a narrow, semi-rigid tube to get past any check valve. Make sure this tube is long enough to reach the bottom of the tank.
Of course, if you’re not concerned about the car, you can punch a hole in the bottom of the tank and capture the fuel that way, but you’ll certainly waste some fuel.
@horse_battery_staple makes an excellent point: If you are uncertain about the quality of the fuel you are siphoning - whether that be because of its age, contaminants (rust/water), or if it has two stroke oil in it, be aware that the vehicle you run the fuel in may run badly, and you may incur mechanical problems, either in the short or long term. Generally speaking, “she’ll run,” especially if you’re cutting the acquired fuel with known good fuel, but you should consider this as an “oh shit” option.
Lots of gas stations don’t bother locking the caps on their tanks. So, get you a bilge pump and some hose, and make sure to wear a mask and hide your license plate.
Hey, I’d never do this, and am not promoting any such thing, but if people are that hard up for gas, don’t take it from random people, take it straight from the gas station.