Wash greens thoroughly, about 3 or 4 times to ensure they are free of dirt and insects.
Prepare the greens by tearing each leaf from its thick center stems; discard stems.
Set collard greens aside until ready to cook.
Combine onions, ham hocks, and garlic in a stockpot; add chicken broth.
Bring mixture to a boil over high heat.
Reduce heat to low and simmer the mixture over medium heat until meat is falling off the bone, about 2 hours (if using smoked turkey, reduce cooking time to 1 hour).
Stir in collard greens, vinegar, Tabasco hot sauce, sugar, red pepper flakes, salt, and pepper into the broth mixture. (You may have to add the greens in batches so that they can all fit into the pot.)
Cover with a tight-fitting lid and cook on low until the greens have reached desired tenderness, about 2 more hours.