The video originally appeared on the man's Facebook page but had since been taken down, 1 News reported.
"I'm sorry for this prank. It never should've happened, the alcohol had really taken effect and I have no sensor when I get this messy," the man wrote.
"There is nothing else that I can say but apologise to everybody, and assure you all it will not happen again."
Despite wearing a shirt with Graham Hill Roofing branding, the man had never worked for the company, a spokesman said.
"We can confirm this person involved has never worked directly for Graham Hill Roofing Ltd, this person was an employee of a temping agency," the spokesman said.
"We are working with the Police to get our clothing back and will assist them with any information they require in this matter."
Fresh Choice Barrington said they had reported the video to police.
"We'll cooperate with their enquiries in any way needed. The person in the video has since apologised and indicated it was a drunken prank."
The store had been "thoroughly cleaned" since the video was made, it said.
"We would strongly discourage any customers [from doing] anything like this in any supermarket."
The coronavirus can spread through coughing and sneezing. Shoppers are expected to keep at least 2m distance from each other during the lockdown, and anyone who is unwell must stay at home.