In order to get sweat stains out of hats, first you will need to identify the type of material that the hat is made.
Make sure not to ignore this step as different materials require different cleaning methods. If it’s a straw hat, try soaking it in water and rub with a little bit of soap.
If it’s a woolen hat, rub it with an old toothbrush and then rinse with cold water. And if the hat is made from leather or synthetic materials, scrub them with a dry brush and then wash them with cold water.
After identifying the material, start using those gentle cleaners like white vinegar and water mix (1:3 ratio) or baking soda (a teaspoon full), which should help remove smelly sweat odor.
For tougher stains, make a paste out of hydrogen peroxide and cornstarch and apply it on wet hat. Leave the paste overnight and then rinse it with warm water.
For really tough stains like mold, using hydrogen peroxide (full strength) can help you get rid of them.
Leave the solution for about ten minutes and then gently scrub the area with a toothbrush.
Even though it may damage some parts of your hat, this step is necessary to remove all bacteria which can lead to further damage of your hat.