By definition, a state of being wet is having water in or on something. So a drink, being a liquid itself, may not even necessarily be classified as being wet; a whole other debate entirely. Since wet is a fixed adjective, anything from damp to drenched can be classified as wet, but the difference is in the extremity of the wetness. Similarly, if someone is dead, they can't get any deader, nor is someone described as half-dead any part dead at all.