Check the care label first
Test any cleaner on a hidden spot
Mix cool water with a small amount of mild detergent
Dampen a clean cloth or soft brush with the solution
Gently scrub the sweat-stained areas
For stubborn stains, apply a paste of baking soda and water
Let the paste sit for 15 to 30 minutes
Rinse with cool water
Repeat if needed
Hand wash the hat if the material allows
Avoid hot water
Avoid bleach unless the care label says it is safe
Air dry the hat
Reshape the hat while it dries
Keep the hat away from direct heat and sunlight
Use a sweatband or hat liner to prevent future stains