Sinckler appeared before a citing panel and was found guilty of "failing to accept the authority of the match official" after swearing at Karl Dickson, his former Harlequins team mate for six years, during Bristol's win over Exeter on Saturday.
The 27-year-old Bears prop said to Dickson "are you f****** serious?" after the official ruled there had been no foul play in a no-arms tackle by England colleague Luke Cowan-Dickie - a decision he reversed after review with the TMO.
Sinckler will be unavailable England's opening Six Nations match against Scotland at Twickenham on February 6 as well as Bristol's next Premiership game.
"Sinckler contested the charge but it was upheld by the independent disciplinary panel, comprising Richard Whittam QC [chair], with Becky Essex and Leon Lloyd, which gave the player a two week suspension," the RFU said in a statement. "He is free to play again on 9 February 2021."
Sinckler has already apologised for the incident on social media.
"Want to apologise for my reaction today," he wrote on Twitter. "Not the example I want to be setting. Heat of the moment stuff. Will make a conscious effort to improve. My bad."
