Recalled New Zealand pace bowler Adam Milne knocked over the top order as India were dismissed for 219 in the third and final one-day international in Christchurch on Wednesday.
Milne and allrounder Daryl Mitchell both took three wickets as the Black Caps employed a seam-based attack to good effect on a green Hagley Oval pitch, needing 47.3 to knock over the tourists.
While the tail struggled, Sundar's composed 51 off 64 balls gave the tourists a chance of squaring the series, which New Zealand lead 1-0.
Milne played in the opening seven-wicket win in Auckland but made way for the second game in Hamilton on Sunday, which was washed out.
He celebrated his recall with a sharp opening spell in which he claimed openers Shubman Gill and Shikhar Dhawan, rewarding captain Kane Williamson's decision to bowl first.
Milne later returned to remove danger man Suryakumar Yadav cheaply and finish with 3-57.
Shreyas Iyer fell to another speedster, Lockie Ferguson, for 49 while Mitchell was a surprise performer with his innocuous medium pace, taking 3-25 off seven overs.
New Zealand are seeking a 14th successive home ODI win to cement their status as the world's top-ranked side in the 50-over format.