Slice the pork shoulder and place it in a ceramic baking dish 48 hours before cooking.
Make the marinade:
Whisk together pineapple juice, Coke, ketchup, soy sauce, brown sugar, garlic powder, salt, and pepper.
Pour marinade over meat, making sure it's well covered by the sauce.
Cover tightly and refrigerate no less than 48 hours and up to 5 days.
When ready to cook, pour meat and marinade into a large saucepot and cook on high until boiling.
In batches, move meat from pot to skillet using tongs and cook until sauce reduces and thickens, and meat cooks thoroughly (about 5-7 minutes).
Serve and enjoy!