BACKSLAP9
Use code BACKSLAP9, in app under offers - have a promo code. I think the voucher will expiry 24 hours from entering code. Includes: 1x FREE Manu Burger voucher. Single use only. No variation allowed. Available only while it is visible on your ‘offers’ page. Offer can be redeemed via App, Website or in-store using your 6-digit code. Not to be used in conjunction with any other offer or discount. Not available on delivery or Kiosk. Offer available for a limited time only while at participating restaurants while stocks last and is subject to change without notice.
I may not have a chance to use this unless it's still available early next week. But this is an old school cheapies type deal that always gets my upvote.