Millman, who is ranked No.155 in the world, waded into the debate on Twitter on Monday night, hitting back at people questioning the practice which he calls ‘a trade secret’.

‘Too much attention on a team member mixing sports drinks … a proper ridiculous notion that something is up, stadium full, cameras everywhere, drinks mixed in player’s box … I mean use a little logic here, maybe just maybe they don’t want to give the edge to anyone,’ he tweeted.

‘To add to that, inside a locker room you see a player’s team always making drinks, in unmarked bottles and put in the fridge. Training programs, supplement intake etc is trade secret.’

Earlier in the week, Djokovic’s wife hit out at online speculation surrounding his on-court energy drinks.

‘I don’t see anything dodgy,’ she said. ‘In fact, I see people trying to be private about their business in a world where everyone feels they have every right to point a camera at you.

YouTube Link; https://www.youtube.com/watch?v=fYKHN9i549E