Apparently some guy went to court with red bull claiming he didn't get his "wings" and didn't feel a energy spike. So, if you have drank a red bull between Early 2014 to Mid 2015, Red Bull will issue you a refund. Not sure if this is 100% real, but it has been featured on USAToday and other popular news websites. You do not need a proof of purchase.
Here's the Link: http://www.energydrinksettlement.com/claim