Sticky infers that it is thick.
Tongue coating, in regards to thickness, reflects general body fluids; or, in the case of when a tongue coating is thick on a specific area of the tongue this indicates a problem with that particular organ system.
Thin means normal.
Thick means too much fluid – therefore Dampness and/or Phlegm. The language we typically use, however, is Dampness. One note of caution: the tongue coating alone cannot tell us WHY there is Dampness. We need more signs and symptoms for that.