Rinse the stain with cold water as soon as possible
Mix equal parts white vinegar and water
Apply the mixture to the stain and let it sit for 15 to 30 minutes
Sprinkle baking soda over the damp stain
Gently rub the fabric together or use a soft brush
Wash the shirt with laundry detergent in the warmest water safe for the fabric
Add oxygen bleach for extra stain removal if needed
Avoid using chlorine bleach on sweat stains, especially if the stain is old
Check the stain before drying
Repeat the treatment before drying if the stain remains
Air dry the shirt until the stain is completely gone
Use an enzyme stain remover for stubborn yellow stains
Pre-treat the underarm area before future washes
Wash white shirts soon after wearing them