Bendtner, 24, was found guilty of improper conduct by European football's governing body after he revealed the logo of a betting company on his underpants in the match on June 13. It was the Arsenal man's second goal of the contest, but Portugal went on to win the game 3-2.
The incident was deemed to contravene UEFA's strict regulations against so-called 'ambush marketing', and as a result handed him a 100,000-euro penalty.
When questioned afterwards about the incident, Bendtner, who spent last season on loan at Sunderland, said: "It is just a pair of lucky boxer shorts that I used in the first game as well and have used before the tournament."
He added: "I didn't know I was breaking any rules but I am aware of that now."
UEFA took a dim view, however, and Bendtner is now set to miss Denmark's opening game in World Cup 2014 qualifying.
The player has three days to lodge an appeal.