Each to their own. Obviously full-time professionals must be careful.
I am a mere semi pro who has been singing for over 60 years   -
skiffle. folk, 50s rock'n'roll, jazz, blues, Americana plus songs for old folks and children.
Depends on the environment - when singing for children and old folks
it is obviously water. In other venues, a good real ale (or three) or red wine. If a sore throat or panic attack occurs, then an Irish whiskey or Southern Comfort always does the trick. But then I am not a full-time professional...…..