SA/SO, NKO/NE/NL/Supreme Ghost, snuck into the recruitment station and went downstaris to get the car battery, threw it towards the wall at an angle to make it not alert the NPC boxing in the training area and fall towards the pool of water below
and waited for the sparks.
I am quite pleased that I managed to find a spot where I can toss the battery without alerting anyone since I the boxer kept on hearing a noise during my test sessions (and was about to give up since it remained stationary anyways).