SA qualifies for quarter-finals
South Africa bowlers Corne Dry (four for 16), Calvin Savage (two for 30) and Solo Nqweni (two for 51) shared wickets between them to skittle out Sri Lanka for 150 in 37.4 overs.
In reply, captain Chad Bowes (46) and Theunis de Bruyn (42) put on 80 runs for the third wicket as South Africa achieved the target in 33 overs.
In the Super League quarterfinal, South Africa will face the winner of the match between England and Nepal.
The other matches of the day saw close finishes, with Ireland getting the better of Nepal in Group A by 14 runs at the Endeavour Park in Townsville, and Afghanistan holding its nerve to beat Scotland by 10 runs at the John Blanck Oval in Group B.