Supporters of US Republican candidate Donald Trump unwittingly helped pick up the tab for a booze-up in Mexico City last night, after they were duped into buying cleverly concealed anti-Trump t-shirts designed by a local brewery.

Trump, who has labeled Mexicans rapists and drug runners, has caused outrage south of the border with his vow to build a border wall that Mexico will pay for - a pledge that inspired brewer Cerveza Cucapa's ingenious scheme to get Trump supporters to cough up for Mexicans' brews.

"It's amazing that we can have a party paid for by Donald Trump!" said 54-year-old Leticia Villanueva, cradling her free beer at the event which had attracted a few hundred people.

It's amazing that we can have a party paid for by Donald Trump!

Late last month, Cucapa, an artisanal brewery from the northern border state of Baja California, posted a video in which representatives went to the United States to hawk blue t-shirts with Trump's face that ostensibly say "I support Donald."

However, unbeknown to the buyer, when they put on the t-shirt, their body temperature adds a clown's nose to Trump's face and alters the message to read "Donald: El que lo Lea," a traditional message meaning "Whoever reads this is Donald."

Proceeds from the tongue-in-cheek publicity stunt helped fund the event on Thursday in Mexico City, where a well-heeled crowd of young boozers in bright yellow Trump wigs took cheer from the property mogul's recent collapse in the polls.

"His campaign is garbage, and the only good thing he's ever done is get us drunk," said 21-year-old Ivan Grajeda. "It's great that he's losing ... that's a triumph for Mexico."

Others hoped that their family in the United States would turn out and vote in the Nov. 8 election for Hillary Clinton, who has strengthened her lead against Trump in recent weeks after her Republican rival faced a string of groping allegations.

"I ask my family members over there to vote for Hillary, as it's not in their interests for Trump to win," said Jose Ramon Trevino, 28. " I have family in Chicago and they are hard-working people, who don't go looking for problems or beg for money in the street."

Esteban Pacheco, a 26-year-old Cucapa employee, said the aim of the brewer's campaign was to build bridges between the two countries.

"We want to unite the people with these types of activities," he said.

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