1. In 3-quart saucepan, heat oil over medium-high heat. Add onion and cook, stirring occasionally, until softened and lightly browned, about 8 minutes. Stir in chili powder, dry mustard, and cinnamon. Cook 1 minute. Add ketchup, honey, orange juice, and vinegar. Bring mixture to a boil and add sliced pork tenderloin. Reduce heat to low and simmer, stirring occasionally, for 15 minutes.
2. Place half of BBQ-pork mixture in a resealable container; cool to room temperature, cover, and place in freezer. Place 4 sandwich buns in resealable storage bag, and store in freezer.
3. Divide remaining BBQ pork among remaining sandwich buns, and serve with coleslaw and pickles, if desired.