Combine the pork, chili powder, garlic powder, smoked paprika, cinnamon, salt, and olive oil in a large bowl and mix well to combine. Cover and marinate in the refrigerator for at least 1 hour or up to 8 hours.
If using bamboo skewers, soak for at least 1 hour prior to cooking. Thread the pork, apple, and onion pieces in alternating layers on each skewer.
Preheat the grill to medium-high heat, and oil the grate. Grill the skewers for about 8-10 minutes, turning occasionally, until the pork is cooked through and the apples are tender. Serve immediately.