By Agence France-Presse
But it is actually a sly act of subversion in the authoritarian state, where this team of political dissidents has turned to football to circumvent government efforts to block their meetings.
The game lasts just 45 minutes before security guards storm the field and kick the players off the pitch -- a regular disruption for a team constantly dodging the watchful eye of the communist regime.
"We have played the so-called mouse-and-cat game with the police and security forces since we established our football team," founding member and activist Nguyen Chi Tuyen told AFP.
The No-U FC squad was formed in 2011 by Tuyen and some 40 others who had rallied against China in a series of protests over disputed waters in the South China Sea, where the two communist countries have overlapping territorial claims.
Police broke up the protests, sometimes violently, and Tuyen said they continued to harass the group when they met at cafes in Hanoi to discuss politics -- a sensitive topic in the one-party state.
"We tried to find out a way to legally and publicly meet each other to discuss everything," said Tuyen, 43, who is commonly known by his online handle Anh Chi.
The football team was formed soon after, named after the U-shaped boundary that Beijing says demarcates its territory in the South China Sea -- and which Vietnam rejects.
"FC" officially stands for football club, though some joke it is short for "Fuck China".
The anti-China cause remains the team's central rallying cry today, with players denouncing Beijing's long history of conflict with its smaller communist neighbour.
But the squad has also embraced a number of other causes, calling for democracy, human rights and freedom of expression in a country where dissent is banned and often punished with lengthy prison terms.
"I joined this football club to support the democracy movement, to call on every Vietnamese to join together and protest the authorities in Vietnam," said Nguyen Trung Linh, a former political prisoner who joined No-U last year.
And though conversations on the field are mostly apolitical -- coffees before and beers after the games are reserved for charged political chats -- the games send an important message to authorities.
"Every match is a protest," said Tuyen, smiling.
In a country where political blogs and Facebook are closely monitored, many activists turn to unconventional means of protest, like art or sport.
"They have to find other avenues to get together and to discuss issues and just to express themselves," Janice Beanland, Amnesty International campaigner for Vietnam, Cambodia and Laos, told AFP from London.
"The No-U team is a classic example of that," she said, adding that even meeting for the matches is "extremely risky".
Most players say they are routinely followed, harassed or even beaten by police or plainclothes thugs.
One teammate was smashed in the face with a brick after a match last year by a group of men he believes were plainclothes police.
Uniformed officers, who did not respond to requests for comment, also break up their matches sometimes.
On a football pitch on a recent balmy Sunday evening in Hanoi, field staff swooped in to block the team's attempt to pose for a picture with a giant No-U flag.
About twenty minutes later, security guards rushed onto the field, tearing the goal net down and ordering AFP journalists to leave.
The officials in charge of the college campus pitch, which No-U had paid to play on for the evening, refused to explain why the match had been cancelled.
"It makes me very angry every time," said Nguyen Van Phuong, 30, who sports a tattoo of the international human rights logo -- a hybrid of a waving hand and a winged dove -- on his bicep.
In order to escape the threat of authorities, they keep match locations secret until minutes before the games and travel in groups to all gatherings.
But the team says harassment has intensified under the country's new conservative leadership in place since last year, a sentiment echoed by rights groups and in diplomatic circles following heavy-handed measures against activists.
Last month a prominent dissident blogger was sentenced to jail for 10 years in a one-day trial over critical Facebook posts the judge branded as anti-state propaganda.
Days earlier another dissident with French nationality was stripped of his Vietnamese citizenship and deported to France.
Since 2015, Human Rights Watch has documented 36 cases of plainclothes thugs physically attacking dissidents -- assaults the watchdog believes are carried out with tacit official backing.
Still, No-U say they will not be intimidated, despite the authorities' continued efforts to shut them down.
"They tried their best for six years but they didn't, they failed," said Tuyen.