How do I reset the EVs gained for a Pokemon?

Solution 1:

Option 1: The 'Reset Berries' are back in this generation, they are acquirable from Berry piles, or from PokePelago. There is a berry for each stat, and they all lower EV by 10 points.

  • HP: Pomeg
  • Attack: Kelpsy
  • Defense: Qualot
  • Special Attack: Hondew
  • Special Defense: Grepa
  • Speed: Tamato

Option 2: New to S&M, you can get 'Reset Meals' from the Festival Plaza. I'm unsure what Plaza level is required for them to start appearing.

Sadly, there is no known equivalent to the 'Reset bag' from XY/ORAS as of yet.