He looks certain to be named in Australia's squad for the World Cup in West Indies and the United States
After being sent into bat, South Africa managed a below-par 160 for six in their 20 overs on a good batting wicket, and the home side reached their target with ease to go 1-0 up in the five-match series.
Lewis smashed seven sixes in a thrilling display of power hitting before he was caught by David Miller at long off from the bowling of leg-spinner Tabraiz Shamsi (1-27).
South Africa’s innings was anchored by an unbeaten half-century from Rassie van der Dussen, who amassed 56 from 38 balls to give them something to defend. The only other score of significance came from opener Quinton de Kock (37 from 24 balls).