Brazil won the friendly with a header from Sandro and a penalty from Neymar just five days before the London Games football competition, which features an under-23 line-up with three over-aged players, kicks off.
Brazil, seeking to win the Olympic title for the first time, sent a powerful message of intent to the other 15 teams in the competition with a silky display in their final warm-up before the Games.
"I am not worried about sending a message to the other teams. My main concern tonight was to get my European-based players, returning from holiday, back in the rhythm of the team," Brazil coach Mano Menezes told reporters.
"That took maybe 20 minutes at the start, but then we played very well for the rest of the half and the match."
On an unusually sunny summer's evening at the Riverside, there was excitement that the Olympics was drawing closer with the theme from "Chariots of Fire" reverberating around stadium before kick-off and the unusual site of the Union Jack fluttering in the breeze.
Britain struck gold in three out of four Games from 1900 but in recent years, fielding a Team GB has been blocked by the Scottish, Welsh and Northern Ireland football associations amid fears that they might lose their independent status within FIFA.
No British team took part in Olympic football since a qualifying defeat to Bulgaria in May 1971 cost them a place in the 1972 Munich Games but when London was awarded the Games, the hosts were obliged to compete.
Friday's match was Britain's only warm-up before the start of their Olympic campaign against Senegal at Old Trafford next Thursday.
Judging on this performance though, coach Stuart Pearce has plenty of work to do over the remaining few days if Britain are going to come anywhere close to the golds they won in the far simpler sporting times of 1900, 1908 and 1912.
Starting with seven Englishmen and four Welshmen including captain Ryan Giggs, Britain looked uncomfortable on the ball and far from a cohesive blend.
They allowed Brazil too much time and space on the ball, and with players like Neymar facing them, that was a dangerous tactic to pursue.
The opening goal came after a lack of communication in the Britain defence, allowing Sandro, who plays in London for Spurs, to loop in a header.
Neymar doubled the lead 10 minutes before the interval when Hulk was tripped by Micah Richards and the 20-year-old striker beat keeper Jason Steele from the spot.
Pearce said the performance proved that Brazil are the favourites for gold.
"They are one of the outstanding international teams around now, let alone Olympic teams or under 23 sides," Pearce said.
"This squad shows how seriously they are taking this tournament, I think they are all internationals apart from their goalie. “They are the team everyone will have to beat if you want to win the gold medal."
As well as the attraction of Brazil and Britain that attracted 24,721 to the ground, a few thousand were also present to watch the afternoon match between Britain's women and Swed
