If the OP was referring to the Coke Freestyle machines, then it was 15 minutes the last I saw. if you get a refill at a bar, then no wait.
I remember two incidents that reminded me of the 15 minute wait. 1. On Freedom, tried to get a Coke Zero, the flow started and after less than a second, that machine ran out of Coke Zero and stopped. Even though I barely got any drops I had to wait 15 more minutes since I started dispensing.
2. I was standing behind the world's dumbest cruiser which coincidentally had a Michigan Footbal jersey on. We walked fast to get to a machine on Allure before I did. When he put his cup up to the machine, it said he had to wait 3 more minutes. He pulled the cup back and I thought he would give me a turn, but he kept putting the cup back to the machine every 5 seconds. I started casually talking to him to see if he spoke/read English. He was oblivious, i talked to him for the entire 3 minutes to see if he would keep doing that. He did.