How do I remove sour smell from towels ?

Just launder with a little bleach if not white. If white use the normal amount. Make sure they are totally dry before folding.

Ask 50 people, get 50 answers. There are many remedies out there and they all do work. You just need to decide what method is best for you. First thing to do is to stop using chemical filled fabric softener and dryer sheets. Here are remedies to try.

https://www.classyclutter.net/how-to-freshen-your-towels-and-get-rid-of-that-mildew-stink-spring-cleaning-day-2/

https://wholelifestylenutrition.com/natural-solutions/how-to-get-rid-of-sour-towels/

https://www.onegoodthingbyjillee.com/how-to-fix-your-smelly-towels-in-3-easy-steps

wash in hot water. use a cup of baking soda & white vinegar in the wash. Also use white vinegar in the rinse. dry completely

Do you have a front loader washing machine? If so, buy Affresh,and run it 3 consecutive times, on hottest cycle. Some washers have a cleaning cycle or a "Pure" cycle, as the Samsung does. Then, once a month, use Affresh. Another tip; Front loaders use very little water, so use just a little detergent, and every so often, use the extra rinse cycle on your towels.

Wash 1st tome with vinegar & baking soda,

2nd time wash with your regular detergent.

Also never leave a wash in the washing machine , overnight !!!!