South Africa have already won the series but will want to make a statement following the loss in the fourth ODI. Sri Lanka, meanwhile, will be looking to continue their fightback.
After falling 3-0 behind in the five-match one-day international series, Sri Lanka made a thumping comeback in the fourth game.
A strong batting performance was supported by a brilliant effort with the ball as the hosts clinched a three-run victory in the rain-affected game in Kandy.
Half-centuries from Kusal Perera, Thisara Perera and Player of the Match Dasun Shanaka took them past 300. Bad weather conditions meant the Proteas' innings was curtailed to 21 overs with the target revised to 191.
A three-wicket haul from Suranga Lakmal led the bowling charge to deny the visitors a 4-0 lead in the series.
The win in Kandy was Sri Lanka's first in 11 ODIs against South Africa, which will give them a world of confidence going into the last game on Sunday.
The pressure has been on the Sri Lankan top-order to perform, and while they were among the runs in the last game on Wednesday, it was again the lower-order offering the heroics.
Angelo Mathews, the captain, has also identified fielding as another area for improvement.
South Africa, who are without the services of injured skipper Faf du Plessis for this game as well, will continue to be led by Quinton de Kock.
Victory in the final ODI will give them momentum to take into the only Twenty20 international to follow, and continue their turnaround after a difficult Test series.
With the series in the bag, the Proteas team management had said they would use the final two games to test their bench.
Reeza Hendricks, for instance, came on to strike a hundred on debut in the third ODI and Heinrich Klaasen was brought in for the fourth.
The talented Aiden Markram hasn't had a good time of it in Sri Lanka so far, and was dropped after the first two ODIs, but in the spirit of experimentation, the team could be tempted to give him another chance to play himself into form.
Once again JP Duminy could be a key player. The left-hander has been in good form in Sri Lanka this summer and his experience will be vital to South Africa's chances in the game.
Duminy tried to mitigate the early loss of wickets in the South African innings in Kandy, but was run out in an unfortunate manner.
He already has two half-centuries in the series, one of which was a brilliant 92 in the third ODI.
There is a possibility of rain in Colombo on Sunday, and the humidity is predicted to be as high as 81 percent. This means the DLS method might be in play once again.
Squads, Sri Lanka: Angelo Mathews (c), Dasun Shanaka, Kusal Perera, Dhananjaya de Silva, Upul Tharanga, Kusal Mendis, Thisara Perera, Niroshan Dickwella (wk), Suranga Lakmal, Lahiru Kumara, Kasun Rajitha, Akila Dananjaya, Prabath Jayasuriya, Lakshan Sandakan, Shehan Jayasuriya
South Africa: Quinton de Kock (c, wk), Hashim Amla, Junior Dala, Jean-Paul Duminy, Reeza Hendricks, Heinrich Klaasen, Keshav Maharaj, Aiden Markram, David Miller, Willem Mulder, Lungi Ngidi, Andile Phehlukwayo, Kagiso Rabada, Tabraiz Shamsi.
African News Agency