$1/1 16 or 20 oz Diet Coke Coupon May 30, 2011 This post may contain a link to an affiliate. See my disclosure policy for more information. Diet Coke released a great new coupon on their Facebook page! Head over there and ‘Like’ them to print a $1/1 16 or 20 oz Diet Coke coupon. This should make for a great deal when paired with a sale! Coupon expires 6/29/11. Available while supplies last. Thanks, Hip2Save!