Rinse cranberries and add them to the pot along with the apple juice (you can set ½ cup cranberries aside if you prefer whole berries in the sauce, otherwise add all of the cranberries to the pot).
Secure the lid, close the pressure valve and cook for 1 minute at high pressure.
Naturally release pressure for 10 minutes.
Remove the lid, stir in the sweetener and mash the cranberries with a spoon if needed (if you reserved cranberries at the start, add them now and press sauté to cook them for a couple minutes).
Turn off the instant pot and let the sauce cool down in the pot (this will also cook the additional whole cranberries a bit).
Taste and add more sugar if needed.
Once the sauce is cool, keep it in an airtight container in the fridge for a week or in the freezer for a couple months.