December 4, 2010 No Comments Free 20 oz. Dr Pepper at Whataburger on Sunday Print out the coupon and redeem for a free 20 oz. Dr Pepper at Whataburger on December 5, 2010. Free 20 oz. Dr Pepper at Whataburger on Sunday – EXPIRED Facebook Twitter Add Comment Notify me of follow-up comments by email. Notify me of new posts by email.