A Smaller Drink

In a time when drinks just keep getting bigger and bigger, I saw a billboard advertising an 8.55 ounce bottle of Coke. I don’t understand this size at all. Either generally or specifically. Soft drinks have been struggling in the US as people try to adopt healthy habits. Does a smaller Coke speak to this trend? It definitely goes in the opposite direction of the popular 20 ounce Cokes. And where does 8.55 ounces come from?