The best and quickest way!
I believe at this time only Scarab or Zippy may have the heart Decal.
Once you unlock the Heart Decal, do not forget to select it on your vehicle.
Go to exhibition, All Star Bots, 1v1. No other mutators are needed.
As soon as the game starts, move out of the way, the bot will hit the ball straight at your goal, as soon as the ball is about to go in, pause the game, swap teams and when the ball crosses the line, achievement unlocked.