Mix together the brown sugar, salt, pepper, paprika, and garlic, and rub over the pork loin. Place the pork loin in the slow cooker.
Combine the apple butter, apple cider vinegar, and mustard in a small mixing bowl and whisk together. Pour mixture on top of the pork loin, ensuring it is completely covered.
Cover the slow cooker and cook on low for 6-8 hours (or high for 3-4 hours). Once done cooking, shred the meat before serving. If you want less of the ‘juice’, remove the pork loin from the slow cooker and shred it in a separate bowl.
Cook the grits according to the package directions. Once done cooking, stir in butter until melted. Once melted, turn off the heat and stir in cheddar cheese until melted.
Serve the grits topped with the shredded pork. Top with more cheese if you’d like.