If you have a Jack In The Box restaurant in your area, grab your mobile phone to take advantage of this great offer! Get a mobile coupon for a FREE Jumbo Jack Burger with the purchase of a large drink when you text the keyword JACKBOX to 43972 and sign up for text messages. You'll receive a reply with a link to your coupon and you'll have until December 31, 2018 to use it. Click here to find a Jack In The Box location near you.