some thick string, like the ones used to tighten pants, get a rather long one.
useless drywall
Step1
place the drywall in the garage or a area of your choice.
Step2
to protect your knuckles, wrap the string around your knuckles makeing sure the rows of the string are in contact with each other, tie it up.
Step3
Beat the dry wall like you never beat before, drywall is the perfect thing to punch, because its sorta cheap, and it doesnt break easily. This reduces your blood pressure AFTER you're done.
Tips & Warnings
when you break it, you feel like a million bucks
use multiple drywalls in a row to improvise for your high strength