- 1). Apply liquid laundry detergent directly onto the sweat stain. Gently rub the detergent into the stain and allow it to sit for 30 minutes. Wash the black fabric as you normally would.
- 2). Mix 1 tbsp. of vinegar with a 1/2 cup of water. Dip a sponge into the mixture and apply it to the sweat stain. This will restore the color and remove the stain and smell.
- 3). Mix 1 tbsp. of baking soda with water until a paste forms. Spread the paste all over the sweat stains and leave it on for 20 minutes, then wash the black fabric as normal.
Source...