South Africa posted 297 for eight in their 50 overs and Australia were well on course after a fast start, until poor shot selection caused their charge to collapse and they finished on 230 all out, losing their last nine wickets for 101 runs.
Australia will welcome the likely return of captain Pat Cummins for the second match in the three-game series in Johannesburg on Sunday, but if this series is a fact-finding mission ahead of the 2027 Cricket World Cup in South Africa, Namibia and Zimbabwe, there will be much food for thought.
The toughest time to bat was in the morning and Australia won the toss and decided to bowl, strangling the South African run-rate early on.
But when Breetzke came in at number four, he played conventional cricket shots to get his innings started, before he found a willing partner in big-hitting Marco Jansen.
Breetzke, who averages over 60 with the bat in his 15 ODIs, scored his 112 from 106 deliveries and Jansen equalled his career best with 75 in 59 deliveries as the pair put on 107 for the sixth wicket.
At one stage South Africa looked as though they may not make 250, so their score of 297 for eight was above par.
Australia started their innings in brilliant fashion as Mitch Marsh blasted 60 from 36 balls and put on 90 in 9.2 overs for the first wicket with Travis Head (36 from 37 balls).
But too many batters threw their wickets away under little pressure and from being well on top in the chase, the momentum changed as wickets slowed the run-rate.
Jansen’s sensational diving one-handed catch in the outfield to dismiss Matt Renshaw (44) left Australia on 215-7, a position they never recovered from.
South African spinners Keshav Maharaj (4-20 in 9.2 overs) and Bjorn Fortuin (2-34 in 8) were the catalyst for the change in momentum with brilliant control.