Update 4/16 @6Pm: It seems the coupons is no longer available for any zipcode. It may have reached print limit already. You may want to check back tomorrow morning to see if they reset the print limit on it.
CVS has Purex detergent on sale buy one get one free this week. Couponsdotcom has a buy one get one coupon available to certain regional areas. Use this coupon to get it free. To find out if the coupon is available in your area, enter your zipcode in the box that pops up when you first visit the site. The BOGO Purex sale ends this Saturday so act quickly.
CVS has been one of the few places where I have had no problems getting free items by combining a BOGO sale with a BOGO coupon. Hopefully, your CVS has well trained cashiers.