the ring is from the wild yeast pellicle. ring is a sign of infection (which you did on purpose in this case).
you added sugar and bottle conditioned? then the wild yeast grew in the bottle, formed a pellicle on the surface of the liquid, fell to the bottom, left a ring.
Tap: Centennial IPA (SMASH)
Tap: Dogfish Head Ginger Saison
Bottle: Stone 11th Anniversary Black IPA clone
Secondary: Flemish Brown Sour Ale