is offering 12oz. Red Bull Energy Drink (Any Variety) for Free when you click the offer and apply your mobile number to receive your 'Tap to Redeem' offer valid for in-store redemption only.
At the redbull website scroll a little bit down and click "CLICK TO REDEEM A COMPLIMENTARY CAN!"
Google voice numbers work, you can get more than one code per number. I used my same number and got 10 coupons. Limit 1 per customer at a given 7/11 though.