equip a food and try to enter again, or swing any melee

- - - Updated - - -

and to refill gas, go to the nearby gas station and press the car horns and wait for the npc to refill it, no it doenst have to be empty to be able to refill it, you can refill it at anytime, and to honk your car equip your car and look to the bottom left of your screen, i assume theres three buttons, press the one below