1. Season chicken with pepper to taste. Place in a 1-gallon zip-lock bag.
2. Add the pineapple with its juice, soy sauce and sugar. Close the bag, removing as much air from the bag as possible.
3. Give the bag a gentle shake to mix everything together. Store in the freezer for up to two to three weeks.
4.Remove from freezer the night before cooking. Place the bag in a large bowl or plate, and set in the refrigerator to thaw overnight.
5. When all the ingredients have completely thawed, empty the bag into a 6-quart slow cooker. Make sure to get everything out, using a spoon or spatula if needed to scrape the bag.
6. Cover and cook on high for 4 hours, or on low for 8 hours.
7. Remove chicken thighs and shred with a fork. Return shredded chicken to the slow cooker and combine with pineapple-soy cooking liquid.
8. Serve with warmed corn tortillas and oven-roasted zucchini.
Optional toppings: Shredded Jack cheese, pickled jalapeno, shredded green cabbage, pineapple salsa.