Prior to the previous games (Sun and Moon), a Pokemon’s Individual Values (IVs) were fixed when you encountered them in the wild (or from an egg). While you could (and still can) manipulate IVs via breeding and other means, if you ended up with a Pokemon with less than stellar IVs, there was nothing to be done about it.
But not anymore! Brand new to these games is the ability to increase your Pokemon’s IVs to their maximum values via Hyper Training.
Once you’re the Champion, Hyper Training can done by speaking to Mr. Hyper at the far end of the Hau’oli City Shopping Mall, to the east of the Battle Buffet. If you’ve never been to the Shopping Mall, it’s the building east from the Pokemon Centre, which only opens its doors after clearing the 1st Grand Trial.
Mr. Hyper is the obvious guy in the middle of the stall, sporting the bright-red shirt. Speak to him and he’ll kindly offer to Hyper Train your Pokemon, but–as with all good things–only if you give him some incentive and the required conditions are met.
Hyper Training is done one at a time for each Pokemon, so if you have multiple Pokemon in need of Hyper Training, you’ll need bottle caps for each of them. If playing normally, bottle caps are pretty hard to come across, making Hyper Training somewhat of a rare luxury.
If it wasn’t clear by now, Hyper Training is fantastic, but depending on how resourceful you are, it can be extremely time- and resource-consuming. Or perhaps even completely out of your league…
Therefore, we only recommend using Hyper Training for Legendary or Mythical Pokemon–basically, Pokemon that cannot breed. Or perhaps some random Shiny Pokemon you found. Instead, you’re better off using your time and resources to breed Pokemon with naturally high (or perfect) IVs.