IP only covers solid objects/dust and water (and a couple of other things if you have extra numbers/letters on the end). Alcohol could still cause deterioration to some kinds of plastic.
I can understand water (pools, toilets, sinks etc.), but how do you hit a small target like a glass? I don't think my phone would fit in a glass...
Regardless, IP ratings, especially on consumer products, are for *accidental* exposure. Relying on them is not recommended beyond stuff like rain, and they rely on all covers being properly installed.