Stains on white clothes are more prominent, and sweat stains are no exception. The protein in sweat causes the stains to appear yellow on your white clothes. While your first inclination might be to bleach the sweat stains out, bleach is the last thing you should use on a sweat stain. A combination of products is all that's needed to successfully remove yellowish sweat stains from your white clothes.
Combine 125 ml (1/2 cup) water, the white vinegar and baking soda in a bowl. Stir well and allow the mixture to foam. Soak the sweat-stained area of your white clothes in the vinegar and baking soda solution for 30 minutes to loosen and lift the sweat stains.
Flush the sweat-stained area of your white clothes with cool water to remove the vinegar and baking soda.
Rub or pour pre-wash stain remover on to any remaining sweat stains on your white clothing. Place the clothing outside, in the sunlight, and allow it to sit for 30 minutes so the combination of stain remover and sunlight can work to remove the remaining sweat stains.
Wash your white clothing, using the hottest water allowed. Hang dry your clothing in the sun until fully dry.
Add 250 ml (1 cup) of white vinegar to your wash water to remove any lingering sweat odour.
Avoid placing your white clothing in the tumble dryer until you're certain the sweat stains have been removed. The heat from the dryer will set any remaining stains.