Edmund took on former world No 3 Raonic for a place in the fourth round of the Miami Open.
And the British No 1 made a brilliant start as he took the first set 6-4.
However, Raonic needed treatment on a back problem three games into the second set.
Edmund took that time to take some water out of his bag and began to rehydrate.
But the umpire would not allow the British No 1 to do so.
That is because the tournament is sponsored by water supplier LIFEWTR, meaning only their products can be drunk on court.
“The water, can you drink a different one,” the umpire instructed.
“There is a tournament sponsor.”
However, Edmund was not keen on wasting time looking for a different bottle.
“Yeah but we’re allowed to wear our [sponsored] clothes,” Edmund replied.
But the official stood firm on his decision.
“Yes but it is different because it is a different ruling,” he said.
“I understand your point.”
Edmund and Raonic are fighting to play defending champion John Isner in the next round.
Isner beat Albert Ramos-Vinolas in straight sets earlier in the day.