Wash the towels together in one load instead of combining them with your other laundry. Use the hot water setting and the amount of laundry detergent recommended for the wash cycle on your machine or the detergent's label.
Stop the wash cycle when it reaches the rinse cycle. Add 2 cups of white vinegar to the rinse water and restart the machine. The vinegar strips the soap residue from the towels without affecting the color or fabric.
Dry the towels on the towel setting of your dryer. Don't use a fabric softener sheet during the dry cycle, as the oils in the softener leave behind a residue that blocks the absorbency of the towels.