The Soweto club, among the front runners for the league title this season, were hit with a suspended 50,000 rand ($7,106) fine after pleading guilty to a charge of spectator misbehaviour and bringing the game into disrepute.
A supporter hurled a handful of stodgy porridge, which South Africans commonly eat with most meals, at the referee at the end of a comfortable away win for the Pirates in Durban in January.
In October last year, arch rivals Kaizer Chiefs were handed a suspended 500,000 rand ($71,060) fine after angry fans threw two plastic vuvuzelas and a cabbage on to the pitch during a cup tie to protest about refereeing decisions.
The throwing of missiles by frustrated fans was a major problem in South African soccer for some time but has almost disappeared in recent years.
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