Hold the clothing under cold running water, and flush the excess chocolate milk off the fabric.
Lay a stack of folded paper towels on a flat surface. Place the chocolate milk stain on top of the paper towels, keeping it facing down.
Dampen a white cloth with dry-cleaning solvent. Pat the back of the stain with the cloth in a rapid blotting motion. Continue in this manner until you have saturated the fabric with dry-cleaning solvent.
Discard the paper towels in a trash can. Place a white towel out flat, and lay the clothing on top of it. Keep the stain facing up toward the ceiling.
Add two to three drops of a prewash stain remover directly to the chocolate milk stain, and rub it into the fabric for several minutes. Wait 10 minutes before laundering the clothing as you normally would.