To get a Subway code for a free cookie, buy something at Subway and fill out a survey at TellSubway.com using information from the receipt. On completing the survey, you receive a code number for a free cookie the next time you visit Subway, as of October 2015.
You must complete the one-minute survey within 30 days of getting the receipt. You must enter the Subway store number, which is on the top left of the receipt, as part of the survey. You also need to provide your email address so that Subway can email the free cookie code to you.