I work as a speech and language therapist for the NHS in England and I do a lot of work on the voice.

The vocal tract is like an engine - keep it lubricated. The best lubricant, in fact the only one I would recommend, is water. Any alcohol is a diuretic, which will be bad systemically, but anything that is red or brown will be worse as it will have a topical drying effect on the mucosa - that's why we call things dry, as opposed to sweet. (Coffee and tea for the same reason, I blame the tannins.) Especially avoid spirits as these will inflame the vocal cords - just inhaling alcohol fumes makes the normally pearly white cords go pink. This means inflammation, increased tenderness - and the cords are as delicate as the whites of your eyes so look after them as well as you would your eyes. Avoid acidic drinks and fizzy drinks as these too will dry the vocal tract. (So no fruit juices or lemonade or carboanted water.) It's just water, water, water. I find no difference between hot or cold water. The very best thing you can do, if at all possible, is to inhale steam as this goes directly to the larynx, whereas drinking water just has a beneficial knock-on effect. Don't put anything in with the water you're steaming from unless you're trying to clear your sinuses or something. Menthol and stuff like that dry the mucosa. Using the engine analogy, don't let the oil run dry then fill it up, but keep it topped up all the time - a mouthful between songs.

Don't use anaesthetic lozenges - they only hide the messages from the vocal cords. If you have a sore throat give it a rest or you will end up with bruised vocal cords and longer term problems than if you had rested the voice for a couple of days.

All of this applies to any professional voice user in any circumstance.

rgds

Phillip