The habit polarised opinion among Rogers' friends.
Melanie Fairweather said minesweeping was a disgusting habit. "I'd rather buy my own drink than steal some random person's slobber."
She said minesweeping was common at house parties but the risks of picking up viruses - or spiked drinks - outweighed the rewards.
Rogers disagreed. "It's fully worth it."
Fellow student Alex Gleed said only a friend's unfinished drink could be a legitimate target. "If it was someone I knew, maybe."
O'Carrols Freehouse manager Sarah Millard said her Auckland CBD pub, like many others, sometimes had homeless folk walk in and help themselves to drinks.
Millard said her pub's compact size let staff keep an eye on patrons and deter most minesweepers.
At Newmarket Cock & Bull, bartender Ashley Nebbeling sometimes caught cheap patrons pouncing on near-empty vessels but she believed the practice was more prevalent at busy nightclubs.
Apart from lost revenue, Nebbeling said bars were concerned about minesweepers getting ill from other people's backwash.
Graduate student Ash McLean said the practice had other dangers. Pub patrons who caught minesweepers red-handed would likely exact revenge. "Aside from hygiene and being date-raped, it'd be confrontation."
McLean said tap beer prices had more than doubled in a decade. "Personally I don't mind shelling out. But if you want to live like that, it's easily done."
Auckland Regional Public Health Service warned against taking drinks from unknown sources.
“There are a range of health risks and diseases that can potentially be transmitted in this manner,” a spokeswoman said.
