Just tossing your cap in the washing machine is not the right way to clean it. Follow this step-by-step process to wash your cap the right way.
Make a bath. Take a tub and fill it with lukewarm water.
Add. Mix some Surf Excel liquid detergent in the warm water.
Dip. Soak the hat in the solution for 20 minutes to allow the cleaner to do its work. If it has a stain, soak it longer; up to a couple of hours if necessary.
Scrub. With a toothbrush, scrub the stained areas. Be careful around stitched patterns and logos. Wash it under cold, running water.
Final move. Air dry your cap