Does anyone have the Full Image in this size? (there's another half of this where you see the rest of the cast bundled up in snow gear, while Ryoko is just in her Bikini. It's fairly comical.)
She actually can't freeze, or be intoxicated by alcohol. It has to do with what her body is made of. That's what made the rest of this picture so funny, everyone else bundled up looking at her like "wtf?"
She can be intoxicated plenty, she's just able to instantly purge it and its effects from her system in an instant. She also doesn't need to eat or drink to survive, and only does so to be social. Nor does she need to breathe.
The downside of not needing to eat/drink is, she also lacks a sense of taste. Literally, she can't taste anything. As a result her cooking skills are... To say the least, lacking.