Synthetic urine had also been used.
Mr Sefton said the level of cheating depended on the type of industry, but most occurred at pre-employment tests.
"The donor is aware that they have a drug test to complete and they come prepared to try and cheat. In a busy week we may have anywhere from 3 to 10 cheats."
Traditionally people have added chemicals such as bleach to urine to try and mask drug use or taken cleansing or flushing pills.
"However we still have a number of people fail the test and get quite upset that the flushing product they purchased hasn't worked," Mr Sefton said.
Workplace drug testing options for companies include pre-employment, random testing, post-incident or accident and reasonable cause testing, where an employee is displaying recognised indicators or patterns of drug use.
Tests are monitored by a technician who stands behind a male donor to ensure the integrity of the sample.
"It is not fully observed, as in the sports drug testing industry, so the employee still maintains their privacy," Mr Sefton said.
There is a different procedure for female donors.
Mr Sefton said the fact people attempted to cheat workplace drug tests was "a real shame".
"They don't seem to realise, or care, that drug testing is all about providing a safe working environment. When they try to cheat the test, they are jeopardising not only their own safety but the safety of others," he said.
Those caught trying to cheat drug tests were usually fired, Mr Sefton said.
"It is a serious issue when someone is willingly jeopardising safety in the workplace," he said.
Mount Maunganui company Ballance Agri-Nutrients carries out pre-employment drug testing on all prospective employees.
Sales and marketing manager Graeme Smith said the test set the tone for the business, making employees aware drug use would not be accepted.
Ballance Agri-Nutrients also test employees following a workplace incident or accident.
"We do drug and alcohol tests after an incident but, at this stage, we haven't got to a point where we're doing random testing. That's not to say that we won't," he said.
Mr Smith said NZDDA had visited all manufacturing sites and conducted drug use identification courses for managers.
While drug testing was crucial for those working with heavy machinery it was just as relevant to the 100 sales representatives driving vehicles on the roads, he said.
Affco director of operations Rowan Ogg said the company's Rangiuru plant near Te Puke also carried out pre-employment testing, post incident or accident testing and testing of those suspected of drug use.
"We operate in a hazardous environment, we've got dangerous machinery we've got many people with knives and it's important that people aren't under the influence of anything," he said.
Mr Ogg said drug dogs were also brought in on a regular basis to check for drugs on the premises, including in employees' motor vehicles.
Affco was also in discussions with the Meat Workers Union regarding implementing random drug testing at its factories, he said.
Mr Sefton said a company wanting to enter a testing programme needed a robust drug and alcohol policy and warned the decision should not be knee jerk or ad hoc.
