There are cars scattered throughout Central Park and you’ll find empty bottles in a number of trashcans. All you need is a bottle that isn’t full, a knife or screwdriver, and a car. I found my knife in the kitchen area in the Museum. With the knife or screwdriver equipped, walk to the back, left side of the car and you’ll have the option to stab the fuel tank by pressing
. Do so, and gasoline will begin flowing out. Equip the bottle and you’ll have another action available by pressing
that will allow you to fill the bottle with gas.