Prepare the Pork: Trim excess fat from the pork shoulder and cut into large chunks. Season with salt and pepper.
Make the Marinade: In a bowl, combine pineapple juice, teriyaki sauce, garlic, ginger, soy sauce, and brown sugar. Whisk until well combined.
Marinate the Pork: Place pork in a resealable bag or bowl. Pour marinade over pork, ensuring it’s well coated. Refrigerate for at least 4 hours or overnight.
Cook the Pork: Transfer pork and marinade to a slow cooker. Cook on low for 8 hours or on high for 4-5 hours, until pork is tender.
Shred and Serve: Remove pork from slow cooker and shred with two forks. Return to slow cooker and mix with cooking liquid. Cook for an additional 15-20 minutes. Garnish with green onions and sesame seeds before serving.