Place the Sharpie-stained jersey in a bucket. Cover the affected areas of the jersey with milk. Allow the jersey to soak in the milk overnight.
Remove the jersey from the bucket of milk. Rinse the fabric with cool water and wring it out.
Lay the jersey on a flat work surface with the Sharpie stain facing up. Squirt white toothpaste onto the remaining stain to cover it. Rub the toothpaste into the ink. Allow it to sit for 10 minutes.
Rinse the jersey to remove the toothpaste. Spray aerosol petroleum-based stain remover on the ink stain. Let it soak into the marker stains for 10 minutes.
Soak the jersey in a solution made with 1/2 cup of oxygen bleach and 1 gallon of warm water. Allow the jersey to remain submerged in the bleach mixture for 30 minutes.
Launder your jersey in warm water, using laundry detergent and oxygen bleach. Before allowing it to air-dry, make sure the Sharpie stains are completely removed. Repeat these steps to remove any remaining ink stain.