The kids respond, the adults respond. There's an eclectic group on this balmy night, from ageing ex-pats to local teens. In this city where there is such a sharp divide between the haves and have-nots, there's something pleasingly democratic about a company director getting a face full of sand when he's cut down by a boy from the favela.
This is Rio Rugby, one of the three biggest clubs in the state, along with Niteroi RFC, from the city of the same name connected to Rio de Janeiro by a 14km bridge, and Guanabara RFC.
It is not being too grandiose to suggest that Rio Rugby is more than a club; it's more like an organic welfare system.
"More than half of our club are from the poor communities of Rio and the other half from the middle classes, including the ex-pats," says New Zealander Dale Smith, one of the driving forces behind the club. "It's a really interesting mix of people. We've had the president of an oil company playing alongside kids from the favelas.
"There's a real sense of helping each other out. If someone has a project on the go, they'll bring in the kids to help and give them some income."
As the practice starts to evolve into match situations, two players stand out. One is a slip of a lad known as Passarinho, which translates to Little Bird.
"He can step you and make you look silly," says Justin Thornycroft, a Zimbabwean national and president of Rio Rugby. "As he's beating you, he'll be laughing at you. You can't help but smile."
The other player is Marcos Paixao, one of four brothers to have played for the club and better known as Careca, which means Baldy, a name given to him on account of his being born without a hair on his body. He now has plenty of it.
Careca, 23, stands out immediately for his speed and power. He wandered down to the beach 12 years ago to see what the fuss was about but wasn't initially enamoured of the sport.
"I was 11 years old. When I first saw it I thought, 'Whoah, that looks violent'," he recalls.
"The next Wednesday, I went down again and this time the people there asked me if I wanted to play. I started training and everybody started supporting me, so I decided this was the game I wanted to play.
"Rugby is already a big part of my life but I want to get to the point where I'm working in rugby, I'm living rugby. I want to be able to make it a career."
Careca has been part of the Brazilian national squad but, at the moment, is on the outside looking in. There is talk around the club that Careca's lack of refinement - the Brazilian national scene is dominated by tertiary institutions in Sao Paulo - might have been held against him, which would be appalling if true. No doubt the raw talent is there.
Cantagalo clings precariously to a steep hillside that overlooks Ipanema and, to the left, Copacabana, but you won't find it on many postcards.
The community - the residents prefer the term to favela, which still carries a stigma - has million-dollar views from overcrowded, unregulated and, in many cases, what we in New Zealand would consider unliveable houses.
The name, Cantagalo, means singing rooster and is a nod to the history of favelas. Brazil was the last country in the western world to abolish slavery, in 1888, and many of the African workers left the farms and the sugar fields to move close to the big cities. They set up rudimentary housing on the edges of the cities and brought their livestock, such as roosters, with them.
In time, the favelas have grown rapidly, particularly after the manufacturing boom of the 1970s, and in many respects are self-contained communities. For a long time, they were run by the drug lords but many of Rio's southern favelas were "pacified" in time for the 2014 Fifa World Cup.
Walk along Cantagalo's narrow alleys and hole-in-the-wall bars and it's difficult to imagine there's a rugby scene bubbling away.
It should be noted that this is not a story about the rapid extension of rugby's reach. Brazil is not suddenly going ga-ga over the All Blacks. There is an acknowledgment that sevens at the Olympics can play a role in exposing the charms of the oval ball to new audiences, but Brazil has its sporting religion and the ball is, and will forever remain, round.
Rather, this is the story of a club and a New Zealander trying to make a difference to the lives of kids who might otherwise remain invisible. That word is chosen carefully, too. On many Rio maps the favelas, despite being home to approximately 19 per cent of the city's population, are not included.
Smith owns the Tiki Hostel in a corner of Cantagalo. It was built with the help of the Paixao family and now brings tourists and travellers into a part of Rio that would otherwise be avoided.
Smith is an ebullient bloke, acting as an unofficial tour guide for the Sky crew while they're in Rio.
Growing up a football player, he switched to rugby in his penultimate year at Kapiti College and, in his final year, is happy to admit he was the worst player in a First XV that included Christian Cullen.
After finishing school, he wasn't ready for university and instead applied to be an overseas exchange student. He ended up in Sao Paulo, where his love affair with Brazil started.
"When I arrived, AFS, the exchange company, gave me a letter I had to give to the family," he explains. "The letter had all the rules but it was written in Portuguese so I didn't know what it said. The dad started reading it out one lunchtime. 'Dale is not allowed to have a girlfriend,' he said, cracking up while showing me the good-looking girl next door. He took me to the garage and said, 'Dale is not allowed to drive,' while showing me the key chain to get access to a car.
"There were all these silly rules and I realised what was going on and just knew it was going to be a great year."
Smith returned to New Zealand and worked for Telecom for seven years. His biggest client was a Swiss guy from Rio de Janeiro, who offered him a two-year contract in 2005.
After the contract ended, he set up an IT company with one of his "brothers" from the Sao Paulo family, started the hostel and hasn't looked back.
He has a partner, Milene, from the capital Brasilia, and a sunny outlook on life that is infectious.
"When I came over here, I'm not sure what made me do it, but I put 'rugby' into Google and Rio Rugby came up. I'd just arrived, didn't know anybody here, so I thought I'd go and check it out. I gained myself an instant family of friends. It's really social here. They've got a girls' team, a vet team, two adult teams - it's really booming and becoming a prosperous club.
"After the game, it's so social but not drunken. It's a fun culture. They'll have a big barbecue, there'll be samba going on and it's just as important as the game. It's just Brazilians being Brazilians. It sounds like I'm exaggerating but if you saw it for yourself, you'd say, 'wow, that's cool'."
When Smith and his fellow club directors saw the potential in kids like Careca, they knew it would make sense to market their club to other kids in Cantagalo, and it spread from there.
"As the project became successful, we decided to formalise it and our president Justin came up with the name 'Nossa paixao e' Rugby' - translated, 'Our passion is rugby'. Passion because of the Paixao brothers who first joined the club from Cantagalo."
Rio Rugby now has an indoor training base in an Olympic-funded centre at the bottom of Rocinha, the city's largest favela, opening up another potentially large catchment area.
Rio Rugby were the first to go into the favelas and set up social projects, but they now have competition, something they don't mind at all, with at least three other clubs following suit.
"When I first arrived in 2005, there were six clubs," Smith says. "There are now 20 clubs in Rio and a federation which works closely with the national administration. We're starting to see things like major sponsors coming through. There's money arriving at the national level but it is yet to filter through to the clubs.
"We're not as organised as back home. It's growing, but it's far from a perfect administrative machine."
Because sevens is about to feature at the Olympics, the media attention on rugby in Brazil is growing. Smith hopes the trickle-down theory of economics will kick in.
If so, rugby in Brazil will benefit. Rio Rugby will benefit. And here's the important part and something Smith and his mates genuinely hope will happen: the kids from the favelas, boys like Careca and Passarinho used to be, will benefit.
Dylan Cleaver was in Rio de Janeiro courtesy of Sky Next.
Sky is the broadcast home of the 2016 Rio Olympics on both Sky Sport and Prime TV.
More stories from Dylan Cleaver in Rio:
Midweek Fixture with Dylan Cleaver: Rio de Janeiro edition
Olympics: Rio's hidden golf miracle
