Marcus Silva, 22, from Dartford, lobbed the missile during his team's 4-1 League Cup defeat at Selhurst Park on September 23.
Six people were arrested as the fourth-round fixture between the south London rivals was marred by crowd trouble.
The Crystal Palace Supporters' Trust later complained about policing of the game, describing attempts to separate fans on the streets around the stadium as a "disaster".
Mr Silva, of New Ash Green, Longfield pleaded guilty to throwing a missile at an area adjacent to a football pitch.
He received a three-year banning order and was ordered to pay £565 at Croydon Magistrates' Court.