How to Wash a Baseball Cap by Hand

Steps
Fill a pan or bowl with hot tap water and just let the cap soak for a while to loosen the dirt.
Fill the sink with water as hot as tolerable and add enough dishwashing liquid or Woolite to make suds.
Scrub the cap with an old toothbrush. This might take a few minutes, but using a toothbrush isn't going to harm any logo or name that might be on the front of it.
Run water over the cap until all traces of soap are gone.
Dry the cap with a couple of white hand towels and pack the inside so as to shape it like it was being worn.
Set it on a bath towel in front of a floor fan. Then in a couple of hours, you'll have a baseball cap as good as new!

Tips
Washing caps in the dishwasher may cause them to shrink or change colors.

Warnings
Be careful the detergent doesn't contain bleach or whitening agents.
When drying the cap, to help prevent colors from bleeding try to use a white towel with white or light colored caps.