A few days ago the Mayor of LA said that people will have to wear a face mask while they're out in public! So a lot of people will be wearing a fabric mask! But obviously you have to do your best to keep it clean!
Popular Science listed some good ways to keep your fabric masks sanitized.
BOIL YOUR MASK
You can boil your mask for 5 minutes. It seems harsh but it gets the job done. If you go this route, it is recommended that you only do it 10 times and then move on to another mask.
WASH YOUR MASK
Washing your mask on hot in the washing machine works well too. Handwashing with soap and water is good as well.
BLEACH...BUT BE CAREFUL
You could also leave your mask in a solution of 1 quart of hot water and 1 teaspoon of bleach for 5 minutes. Be careful if you do this. PopSci says too much bleach could damage the mask. You also want the mask to be free of any bleach when you put it on to prevent you from inhaling the fumes. That can be damaging to your respiratory system.