Make an excuse for it, like, "I'm sorry, but I require medicine."
Then take the potion with your back turned. Then be a headless mofo.
Too conspicuous.
Cough roughly, as in,
very roughly, then kneel for a bit, and drink from the bottle.
Then drop the bottle, make sure the glass shatters for some nice effect.
Express your regret as to why you can't take your hood off.
And if they force you, then
be a headless mofo.