As well as from pumps, you can siphon gas from other vehicles using a hose and a gas can (or other container). Gas cans can usually be found in garages, in the back of cars, at auto-shops ...

You can hold down ‘RT’ to siphon gas from the wreck ... Once you’re back at Oppy’s Auto Shop, I recommend using the gas pump against the wall beside the parking spot indoors to fill ...