Thoroughly rinse your collard greens in cold water at least three times to remove all grit and sand. Stack several leaves, remove the tough center stems, and chop into 1-2 inch pieces.
In a large pot or Dutch oven, heat olive oil over medium heat. Add diced onions and sauté for 3-4 minutes until translucent. Add minced garlic and cook for another 30 seconds until fragrant.
Add your smoked turkey pieces to the pot, followed by red pepper flakes, salt, and black pepper. Allow the meat to heat for about 2 minutes to release its smoky essence into the oil.
Add your chopped collard greens to the pot in batches, allowing each addition to wilt slightly before adding more. Pour in enough chicken broth or water to just cover the greens. Stir in apple cider vinegar, sugar, and hot sauce (if using).
Bring the pot to a gentle boil, then reduce heat to low, cover, and simmer for 60-90 minutes, stirring occasionally. Your greens are done when they're tender but still have a slight bite.