If my character simply "upends his glass", does it mean he drinks it's contents or that he spills it onto the table? Do I need to specify that he drinks the whiskey after having performed the previous action for him to actually be drinking it?
With that sentence: I'd assume he downed it. means he poured it on the bar. Needs some context, IMHO.
There is a special place in hell for people who spell Whisky with an "e" in it!! If I am being honest I am unsure what "upends his glass" means! If you want the dude to be drinking from the glass then simply put "took a sip" or something of that nature!
From what I've read, "whiskey" with an "e" refers to drinks produced outside of the British Isles (to include, for the purpose of this discussion, Ireland), and "whisky" is from the aforementioned places. I'm generally a bourbon man, but I appreciate a wee bucket of Scotch or Irish whisky from time to time.
"Whisky" is the Scottish spelling, but there are no correlations, laws, or styles governing the spelling. Americans do either depending on the whim of the distiller.
Just spell it "Uisge," you heathens. Getting back to the OP, I agree with Ian. You don't need to specify--the surrounding context of the scene should make it clear.
Uisce beatha, thank you. That's literally the only proper form of address. As to the OP, sure, it should be pretty clear from context.