One more thing I'd like to add from my own experience: sugar free hard candy.

Forget about mentholated cough drops, and all the so-called throat "soothers" -- what they really do is constrict your throat, and leave you with LESS of a singing voice.

Also, sugar has a tendency to dry up your throat.

When I sing professionally, I introoduce myself as "Matt don't-quit-your-day-job Bram" -- referring to the fact that my voice is no great joy to begin with, so I need all the help I can get. That's why I keep a full supply of candies in my guitar case, available for an instant voice improvement.