Another thing you can do instead of pushing a car is pulling a car. My old squad leader stole a harness or acquired a should say a harness from Airborne School. Basically you hook the harness onto the front of a car or truck and also hook a rope onto the back of a car or a truck. You then hook yourself into the harness and try and sprint about 50 meters with it. You may need a guy behind the car or truck to spot you and obviously someone steering the car.
Well anyway you sprint 50 meters or if your sucking walk pull it 50 meters and then unhook your self and go to the rear of the vehicle. You then grab the rope and pull it back 50 meters for a cool down. I know this is gonna sound crazy but it is easier to pull it back than it is to pull it forward.
Anyway my Squad does this as part of a circuit training. You can have your other dudes doing other excercises while the guy is pulling the car. Like we have a kettel bell excercise, dips, crunches, sand bag carries up a short flight of stairs, and jump roping. All these guys keep working till the guy pulling the car is done. Then you switch it around till everyone pulls the car 4 times. Usually takes about 1 hour, but it is awesome and smokes the shiit out of your joes.