This is the way i did it
Go to any drinks machine and choose a drink (doesnt matter what one)
Make it bigger and look up
Try to drop it as high as you can (preferably so it hit the ring pull end)
It should land and burst the can, spraying its contents everywhere
Thats how i did it, i picked up a can, randomly looked up and dropped it and carried on walking, it banged and hissed then it popped up for me
(my first ever TA Guide!)