In a large skillet over medium-high heat, cook the chopped bacon until it’s halfway to crispy.
Add the garlic and onions and sweat until the onions are translucent, constantly stirring to keep them from burning, about 4 minutes.
Add the collard greens, chicken stock, apple cider vinegar, red pepper flakes, salt and pepper, and stir. Reduce heat to medium. Cook for 15 minutes, stirring occasionally, or until collard greens are wilted and the chicken stock has reduced.
Taste and adjust seasoning to your liking. Serve hot.