Four fire appliances were called to the Stuart St store at 6.30pm following reports of a small fire near the stairwell on the first floor, Dunedin Fire Station senior station officer Lindsay Rae said.
"The fire sprinkler did an excellent job on containing the fire because, without it, it would have been much worse."
Fourteen firefighters attended the blaze, with eight donning breathing apparatus to put out a small fire and help with the "salvaging of stock".
"It was very smoky in there and there will be some stock damage," he said.
Mr Rae declined to say what caused the fire but confirmed it was centred near a drink vending machine.
No-one was in the building at the time but "shocked" staff arrived later, he said.