It’s disgusting, but a reminder anyone in the food biz is only as good as their worst front-line employee.

The New York Daily News reports a South Carolina McDonald’s worker served customers some Sweet Tea with a side of phlegm.

The incident happened on Saturday when a mother and daughter noticed their tea wasn’t sweetened and returned their drinks in exchange for the correct order, police told WYFF-TV.

When their teas were returned, the duo saw their order wasn’t correct again and were heading home to add their own sweetener. But when they looked in the drink, they noticed both had an stomach-turning side of phlegm floating on top.

Instead of going back to McDonald’s, they went straight to the police station.

"It’s a health issue," Greenville County Sheriff Deputy Laura Campbell told the TV station. "When it becomes bodily fluids you know people have all kinds of contagious viruses and diseases."

Cops nabbed 19-year-old Marvin D. Washington Jr. and charged him with unlawful and malicious tampering of the food, according to the report.

In a statement to the TV station, the franchise owner of that McDonald’s location said his restaurant "has the most stringent food safety and quality standards" and urged customers not to jump to conclusions.

"Nothing is more important to me than the safety and well being of my customers," he added.