A man who ordered an iced tea at McDonald’s claims he was given marijuana and inadvertently got high for the first time in his life when he drank it.

Parrish Brown from South Carolina in the US ordered a meal and a sweet tea with light ice and extra lemon at a McDonald’s drive-thru on Hilton Head Island.

But after he slurped it down at work he became “high as a kite”, the Island Packet newspaper reports.

Brown believes the “extra lemon” in his order was a secret code word for cannabis.

A McDonald's customer claims he got "high as a kite" for the first time in his life because his drink came with some extra herbs. Stock image. Credit: Getty Image

“I have never had weed a day in my life, so immediately after I started drinking it, I started to feel weird and it didn’t taste like something I recognised,” Brown said.

The 24-year-old said he kept drinking the iced tea as he needed a thirst-quenching drink at work.

He eventually opened up the cup to find three bags of cannabis, which had become punctured when he was poking around with his straw.

“Well, I was high and panicking and at work, so I called my dad,” Brown said.

“I didn’t want to get in trouble for this.”

Two Aussie mates had to be talked out of the gnarly honour of eating what they claim is the world's oldest burger, which they bought at an Adelaide McDonald's 20 years ago.

Brown said the rest of his meal, which included 10 chicken nuggets and a double cheeseburger, was completely normal.

He claims the McDonald’s worker paused as he ordered the iced tea, saying back “extra lemon?” in an odd voice.

Once Brown realised he was drug-affected, he called his dad, who told him to call the police, and it was “a whole ordeal.”

“And then, it gets worse,” Brown said.

“I called dispatch and the woman yelled like ‘What!? Call 911!’. And I was like, ma’am, you are 911. She couldn’t believe it.”

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Brown said he had a hard time convincing his manager and authorities what happened.

Parrish Brown claims a McDonald's worker gave him cannabis in his drink. Credit: Getty

A police officer took one sniff of the drink and knew what it was.

“The officer asked me why I drank it and I was like, ‘Well, I was thirsty!’” Brown said.

Brown said he paid the regular price for the items. Police are investigating the incident.