You should make most if not all of your progress towards this by playing for the other achievements.
If this is your last achievement, however, the quickest way to finish games is to time yourself out. Spawn yourself on one of the extreme edges of the map (I find the east coast by the castle and beach drag strip works well) and it shouldn't be long before the arena shrinks past you (check the map to see the shrinking ring.) Now just sit there and wait!
If you end up spawning in a safe zone, either drive out of the arena or purposefully lose a head-to-head if you happen to meet another player.