The Earl of Strathearn and Prince Harry were in Gorbals Leisure Centre meeting coaches from the Coach Core programme.
As Prince William took instruction from a football coach, his younger brother showed off his boxing skills.
The pair then played a five-a-side match with Harry's team romping to a one-nil victory - much to his brother's annoyance.
William and Harry joined about two dozen young people on the sixth day of competition at Glasgow 2014.
They watched a warm-up session and joked and laughed with the coaching apprentices as they threw themselves into skills workshops.
The royals are attending Glasgow 2014 for a second day after enjoying the gymnastics and boxing yesterday.
Along with the Duchess of Cambridge they made an appearance at the hockey before watching Wales take gold in the women's 800m freestyle final at Tollcross Swimming Centre last night.
Today, William was cheered for his skills on the pitch after coming out tops in a dribbling competition.
Meanwhile, Harry got physical sparring with some of the programme's boxing apprentices.
The brothers then faced off on opposite sides of a five-a-side game, jostling each other jokingly.
Harry's team was victorious with a 1-0 scoreline.
Goal scorer Lauren Weir, 21, from Glasgow, specialises in taekwondo and said it was only the second goal she had scored in her life.
She said: "Prince Harry set me up for it and gave me a high 10.
"I said to Prince William 'hard lines, better luck next time' and he found that quite funny."
Of the royals' footy skills, she added: "They were saying they were rubbish but they're not too bad."
Nathan Bawuah, 21, a judo coach who recently completed the programme in London, sparred with Prince Harry and drew 2-2.
He said: "He was very nimble, which I didn't expect. He made me sweat so much.
"They were really down to earth which was really surprising."
Of his visit to the Games, he said: "Glasgow is the friendliest place I've ever been - everywhere people are smiling and asking how you are.
"The atmosphere is second to none."
Gillian Sloey, 20, a footballer from Glasgow who spoke with the Duke, said: "He did say he is quite competitive.
"It was a pleasure meeting them and great to see them getting involved and having fun.
"They had smiles on their faces most of the way through."
Asked how she would rate their skills on the pitch, she said: "I was really impressed."
On the Games themselves, she said: "The atmosphere is amazing. It's a really exciting time for sport."
At the end of the visit William and Harry joined all the young coaches for a group portrait.
The project was launched by the brothers and the Duchess of Cambridge in July 2012.
It offers young people a chance to gain work experience and training in community sports coaching.
Across the city, Kate attended a reception hosted by SportsAid.
The Duchess is patron of the charity, which funds the rising stars of British sport to help them reach the top and compete internationally.
At the event at Home Nation House she visited mentoring sessions led by tennis player Laura Robson, former world champion open-water swimmer Keri-anne Payne, Glasgow 2014 Team Wales captain Aled Davies and 2002 Commonwealth Games silver medallist Steve Parry.
She also watched as rower Joshua Armstrong, 16, from Hamilton, South Lanarkshire, and cyclist Jack Carlin, 17, from Paisley, Renfrewshire, gave live demonstrations of their sports.
Guests at the event included former world and Commonwealth champion swimmer James Hickman, London 2012 Paralympic sprinter Sally Brown and world champion track cyclist Becky James.
More than 450 of the athletes competing at Glasgow 2014 have had support from SportsAid, including Sir Bradley Wiggins for Team England, Daniel Keatings for Team Scotland, Michael Conlan for Team Northern Ireland and Geraint Thomas for Team Wales.