"So I hope to God you don't get thirsty on your next shift because we just wouldn't be able to allow a drink," the message said.
The manager wrote that most crew would not qualify for the paid break given many work shy of four hours, so banning them from taking any breaks was reasonable because "fair is fair".
The social media tirade was apparently sparked by requests from some staff to take the break, with the manager writing: "We go above and beyond … are we really such bad guys? Honestly!"
The message began: "As we all LOVE the legislation and are all clearly so hard done by … let me clarify for you the below ENTITLEMENT!
"We are more than happy to go with the standard 10-minute break policy … for those crew who are all over Facebook tagging each other and commenting."
Tantex Holdings is operated by Tanya Manteit-Mulcahy and her husband Terry Mulcahy, who own McDonald's franchises at Central Station, the Myer Centre, Queen Street Mall, Wintergarden, McWhirters and Windsor West in Brisbane.
The paid breaks are part of an existing workplace agreement and McDonald's franchisees have faced pressure from the Fast Food Workers' Union to pass on the entitlement.
Following the message being leaked, the union fired back and organised a protest outside the company's Queen Street Mall outlet — said to be the largest in the Southern Hemisphere.
"If treating your workers like dirt is their business model, they don't deserve to employ anyone," the union said.
"We're not having a bar of it. This is how McDonald's treats young workers far too often. It's time McDonald's Australia took responsibility for the way (the country's) youngest workers are being exploited in their outlets."
The union also said the message was "wrong on many fronts" and that any worker rostered on a four-hour shift was entitled to the paid 10-minute break.
A McDonald's Australia spokesperson said any employees with concerns about their conditions should contact a "dedicated employee assistance hotline".
"Everyone who works in our restaurants is given breaks as required," the spokesperson said.
"We work closely with our restaurants to ensure all our employees receive the correct entitlements and pay."
News.com.au requested comment from Manteit-Mulcahy and Tantex Holdings but had not received a response.