Sinclair, who scored 190 goals for Canada over 23 years, came off the bench to a standing ovation ahead of her planned international retirement as the hosts dominated a heavily rotated Australia in the first of two friendlies.
It was the first time the two teams met since Australia beat Canada 4-0 at the World Cup in July.
Australia head coach Tony Gustavsson made nine changes to the line-up that beat Taiwan in the Olympic qualifiers last month, handing debuts to Charlie Rule and Sarah Hunter.
The visitors did not have any shots on goal in the first hour as Canada's Nichelle Prince found the net twice in the first-half before Cloe Lacasse, Simi Awujo and Adriana Leon scored early in the second-half.
The tide turned when Gustavsson brought on Manchester City's Mary Fowler, Arsenal's Kyra Cooney-Cross and other experienced internationals after the fifth goal.
The World Cup semi-finalists did not concede for the rest of the game and had one shot on target towards the end.
Australia will play Canada again on Tuesday as they continue to build up to February's Olympic qualifier double-header with Uzbekistan.
The friendly in Vancouver will be Sinclair's final match for Canada.
