As many as eight glasses a day.
That is how much hard liquor KTV hostesses say they may end up drinking in a night to keep customers happy and, for many, to earn more money.
"Nobody forces you to drink," said Ms Ching, a svelte 24-year-old hostess from China.
"But customers who are drunk are likely to give you bigger tips," added the Hubei native.
Hostesses who spoke on condition of anonymity told The Sunday Times they can earn about $5,000 a month chatting, singing and playing drinking games with customers.
Tips can sometimes balloon to $800 on a good night.
Questions have been raised on how much nightlife workers drink on the job after the recent death of 27-year-old Kim Seoa.
The Sunday Times understands that the South Korean was an agent who brought hostesses to Singapore. She had accepted a challenge to drink as much liquor as possible after a customer offered to pay her $50 a glass.
On May 13, after drinking 18 glasses which would have earned her $900, she collapsed.
She later died in hospital.
Her family soon arrived from Seoul to claim her body, according to Chinese evening newspaper Shin Min Daily News. Police are investigating the case.
For most who work in KTV lounges, the pressure to drink is real. Mamasans and managers are keen to promote cognac or whisky, which they sell for more than $200 a bottle at a fat profit margin.
Some girls get a cut on the sale of liquor, while others supplement their pay through tips.
For some hostesses, sex is part of the mix. They told The Sunday Times that some mamasans take a cut of the sex money as a "fee" for hooking them up.
"Some customers want you to drink five glasses to prove that you can drink, before they let you sit with them and earn their money for the rest of the night," Ms Ching said. "If you refuse, the money will just go to more willing girls."
Drinking games are popular and often lead to more alcohol being consumed.
The dice game, in which players try to call each other's bluff, is a favourite of customers. The girls have to drink each time they lose.
Some customers let them drink alcohol diluted with ice or mixers. Others insist that the shots are drunk neat.
Sometimes, the girls would try to get the men to drink from their glass, often flirtatiously. "I try to pour less or distract the customer with small talk," Ms Ching said.
A mamasan in a high-end club said the hostesses are expected to use their discretion, adding: "They should know their own limits, and take care of themselves."
According to medical guidelines, Asian women, who generally have lower blood volumes and lower levels of enzymes to break down the alcohol in their system, should take only one drink a day.
This equates to a can of beer, a glass of wine or a shot of hard liquor. Men generally can take twice as much.
Gastroenterologist Yim Heng Boon warned that heavy drinking can lead to liver inflammation and increase the risk of liver cancer. Drinking eight glasses a day means "the risks of getting liver problems are very high", he added.
Mr Dennis Foo, president of the Singapore Nightlife Business Association, said of Ms Kim's death: "Downing 18 glasses of spirits at one go is way beyond anything I have ever heard in my 35 years of business.
"It was very irresponsible of the customer to use money to entice the lady to do so. Operators should be wary of such customers."
The association has advocated responsible drinking on the nightlife scene for many years, he added. The police have a handbook for nightlife operators to deal with difficult situations, he said.
Ms Crystal, a hostess from China, said she is aware of the dangers, but the lure of fast money to spend on clothes, bags and shoes keeps her in the job.
"Drinking is part of the job, you have to 'show face' and keep the customer happy," the 27-year-old said.
"But I don't intend to do this my whole life. One more year and I'll quit. Hopefully, my health will not be too bad yet."