Rangers fan James Adamson hurled the device from a packed stand in celebration after his side scored against Motherwell at Fir Park.
Sheriff Andrew McIntyre branded his actions “stupid, dangerous and extremeley reckless”.
Adamson (20), of Whitburn, West Lothian, appeared at Hamilton Sheriff Court where he admitted a charge of culpable and reckless conduct on January 28.
The court heard he was caught on CCTV lighting a smokebomb and throwing it from the South Stand which was full with 4000 Rangers fans. Rangers won the league game 2-0.
Defence agent Vincent McGovern said the device was not recovered by police. It landed on an ash area between the pitch and the stand, and there was “no one in the immediate vicinity”.
Mr McGovern described his client as an “over enthusiastic” Rangers fan who is also a “talented junior footballer” and a coach to under-12 age group players.
The solicitor added: “As a result of this incident Rangers withdrew his season ticket.”
Adamson, who works as a greenkeeper, has a previous conviction for a football-related offence and Sheriff McIntyre said he could easily have been locked up this time.
However, the sheriff ordered him to do 150 hours of unpaid community work instead and imposed a 21-month football banning order.