Fill your bathtub approximately half-full of warm water.
Pour one-half cup of non-detergent soap into the water, and use your hand to mix the soap around in the water.
Place your sleeping bag into the tub, and rub the fabric together all over the bag to massage the soap and water into the bag.
Allow the sleeping bag to remain in the soapy water for 15 minutes.
Drain the water and soap from the bathtub, and press the bag gently to remove extra water.
Fill the tub half-full again, but do not add soap this time. Massage the bag again to release soap that might still be in the bag from the wash.
Allow the bag to remain in the cold water for 15 minutes.
Drain the water again and press the excess water out of the bag once more.
If you still see soap coming out of the bag, repeat Steps 6 and 7 until all of the soap has been removed.
Hang the bag over a clothesline in a sunny, well-ventilated area until it is completely dry.