A tour that started with an unexpected Test series triumph ended with a second successive limited-overs series humiliation for Sri Lanka when South Africa won the third and final T20I on Sunday.

South Africa made a daunting 2-198 and Sri Lanka were beaten by 45 runs according to the Duckworth-Lewis-Stern method when they were bowled out for 137 chasing a reduced target of 183 in 17 overs following a rain delay at the Wanderers Stadium.

It completed a 3-0 series sweep for South Africa, who also won a one-day series 5-0.

"In home conditions, South Africa are very tough," said Sri Lankan white-ball captain Lasith Malinga, who only joined the tour after Dimuth Karunaratne led the Test side to a 2-0 series win.

Malinga said his side's inability to make early bowling breakthroughs, together with their own poor top-order batting, had been the main reason for their defeats.

"Going forward we realise what we need to do," he said.

South Africa's match-winner on Sunday was allrounder Dwaine Pretorius, who took advantage of a promotion in the batting order with a power-packed innings of 77 not out off 42 balls.

He followed up by breaking a rapid Sri Lankan first-wicket partnership of 42 when he trapped Dhananjaya de Silva with his first ball.

Opening batsman Niroshan Dickwella raced to 38 off 22 balls and Isuru Udana played another hard-hitting lower-order innings, hitting four sixes and making 36 before Sri Lanka lost their last four wickets for no runs.

South African captain JP Duminy said Pretorius and opening batsman Reeza Hendricks made possible an all-out assault in the closing overs with their batting in the first ten overs.

Pretorius and Hendricks (66) put on 90 for the second wicket before Duminy joined Pretorius in an unbeaten third-wicket stand of 71 off the last five overs. Duminy made 34 not out off 14 balls.

Sri Lanka suffered another top-order collapse, going from 0-42 to 5-79 and 6-96 before Udana’s late aggression.

Andile Phehlukwayo took 4-24.

Hendricks was named man of the series after making a second successive half-century.