/e produces a battered silver flask.
/run ToggleSheath()
/drink
This macro will make your character do the drink animation with a little more flavor. The second line toggles weapon sheathing, but this never occurs due to the animation being canceled by the drink command. It is just to add the sound effect of drawing the weapon, as if producing the flask had made a sound. Feel free to change the first line to describe your flask, wine-skin, or the like however you want.