The only way currently is to use PKHex. That will require you to have a New 3DS with the Homebrew channel installed (not 2ds or o3ds) or any 2ds or 3ds with CFW. You'll need that so you can backup and restore your save files... which will allow you to use PKhex.
Also, I will be listing some Unlocked Sun and Moon games in the store here in a few days... so there is that. And also in a day or two I'll be selling 2DS units with CFW which will allow you to hack Sun and Moon (and do a million other amazing things!).