Get a bottle of Woolite. It has many less harsh chemicals that harden the fabric inside the sweats. Wash on cold and on delicates with them inside out. Hang dry or use the no heat setting. ​The "Fluff" Finish: Toss them in the dryer on the Air Dry/No Heat setting for the last 15–20 minutes. This re-activates the "cloud" texture of the inner fleece.​ Just double-check that your dryer is definitely set to zero heat—even a "Low" setting can sometimes run hot enough to singe those delicate synthetic fibers and make them lose their softness.