Step 1: Materials
The first and only thing you will need is a pair of large (clean!) men's briefs.
Step 2: Tools
The only tool that is necessary is a pair of scissors.
Step 3: Cut a Hole in the Crotch
With your scissors, cut a U-shaped hole in the crotch. This will result in a hole to stick your head through.
You now have a super-cute sports bra that you can exercise in!
Step 4: Workout
Put it on and go get your workout.