An employee at a McDonald’s in Pennsylvania, a key battleground state, showed Mr Trump how to dunk baskets of fries in oil, salt the fries and put them into boxes using a scoop.
Mr Trump, a well-known fan of fast food and a notorious germophobe, expressed amazement that he did not have to touch the fries with his hands.
“It requires great expertise, actually, to do it right and to do it fast,” Mr Trump said with a grin, putting away his suit jacket and wearing an apron over his shirt and tie.
The visit came as he tried to counter Democratic nominee Kamala Harris’ accounts on the campaign trail of working at the fast-food chain while in college, an experience that Trump has claimed, without offering evidence, never happened.
A large crowd lined the street outside the restaurant in Pennsylvania. Later he was attending an evening rally before catching the Pittsburgh Steelers home game against the New York Jets.
After serving bags of takeaway to people in the drive-thru lane, Mr Trump leaned out of the window, still wearing the apron, to take questions from the media outside.
The former president, who has constantly promoted falsehoods about his 2020 election loss, said he would respect the results of next month’s vote “if it’s a fair election”.
He joked about getting one reporter ice cream and when another asked what message he had for Ms Harris on her 60th birthday on Sunday, Mr Trump said, “I would say happy birthday Kamala”, adding: “I think I’ll get her some flowers.”
Mr Trump did not directly answer a question about whether he might support increased minimum wages after seeing McDonald’s employees in action but said: “These people work hard. They’re great.”
He added that “I just saw something, a process that’s beautiful.”
When aides finally urged him to wrap things up so he could hit the road to his next event, Mr Trump said: “Wasn’t that a strange place to do a news conference?”
Mr Trump has long questioned Ms Harris’ story of working at McDonald’s and has fixated in recent weeks on the summer job she said she held in college, working the cash register and making fries at McDonald’s.
Mr Trump said the vice president has “lied about working” there, but offered no evidence for claiming that.
The vice president rejected Mr Trump’s claims, saying she did work at the fast-food chain four decades ago when she was in college.
“Part of the reason I even talk about having worked at McDonald’s is because there are people who work at McDonald’s in our country who are trying to raise a family,” she said. “I worked there as a student.”
