Add the brown sugar, paprika, chili powder, garlic powder, black pepper, and sea salt to a small bowl. Mix to combine.
Cover the cubed pork in the spice rub.
Set pressure cooker to the sauté setting and add the oil. Once hot, add the cubed pork and brown on each side—about 3 minutes. You will probably need to do this in 2-3 batches. Place pork on a clean plate after browned.
With a wooden spoon, scrape off the browned bits. You can add a tablespoon of water or two to help scrape up the browned bits if needed.
Whisk together 1 cup of the BBQ sauce, apple cider vinegar, and water.
Set the pressure cooker to the Pressure Cooking setting. Add the browned meat and the BBQ sauce mixture to the pressure cooker. Stir to combine.
Twist on the top and make sure the valve is at "sealed." Cook on high pressure for 45 minutes.
Let naturally release for 10 minutes, and then put the valve on quick release.
Turn pressure cooker off and carefully remove the top.
With a slotted spoon, remove the pork to a large bowl—leaving the liquid behind.
Either shred the pork or cut into smaller chunks.
Mix with the remaining 1/2 cup of BBQ sauce.