It was also the fastest 50 by a New Zealander, eclipsing the 20-minute-old record set by Guptill who took 19 balls to get there at the top of the innings.
Guptill was the only wicket to fall in the New Zealand innings, out for 63 off 25 balls with six fours and five sixes, while Munro clouted seven sixes and one four.
It took New Zealand exactly 10 overs to mow down the modest 143-run target with Kane Williamson unbeaten on 32.
The victory gave New Zealand a clean sweep of the tour by Sri Lanka, winning the Twenty20s 2-0 to go with their 2-0 domination of the Tests and 3-1 win in the one-dayers.
As has happened throughout the tour, the Sri Lankan top order failed to click. After being sent in to bat, they were all out for 142 with only Angelo Mathews showing any resistance with an unbeaten 81.
It was Mathews’ highest score in the shortest form of the game, easily eclipsing his previous best of 58 against England five years ago.
Tillakaratne Dilshan with 28 was the only other Sri Lankan to reach double figures as the wickets tumbled.
Sri Lanka’s downfall was as much a result of poor shot execution — repeated ill-timed slogs — as it was good bowling and fielding by New Zealand.
The chief destroyer for New Zealand was Grant Elliott with four for 22 in his first game back at Eden Park since his six off the penultimate ball against South Africa to get New Zealand into the World Cup final last year.
Adam Milne and Mitchell Santner, who replaced Matt Henry and Ish Sodhi in the New Zealand line up, took two wickets apiece.
Faced with an undemanding target, Guptill and Williamson starting in rollicking form.
The 50 came up in 22 deliveries and the 100 in 43.