New to doing this so hopefully I'm doing this right. Onecard sent out an email to targetted people offering them one free 1.5L coke no sugar when they swipe their onecard. It works as I've picked one up. Just search your emails/spam and see if you have one too
Terms and conditions (as per email)
The offer is effective from 03rd December – 30th December 2018 ("Promotion Period"). Offer is not available online and can only be redeemed once. Offer applies to one COCA-COLA No Sugar 1.5L only. Available while stocks last. Range may vary per store. This offer is only available to those customers who have received communication directly from Countdown. This communication will be via email sent by Countdown. The offer cannot be shared with another person by forwarding the email. The email may need to be shown to checkout staff at the time of redemption to ensure validity.