Drinking either hot or cold water will stun and stress out the vocal chords. A cold drink will cause your throat to become stiff. This is why room-temperature or warm drinks are recommended before singing to keep your voice healthy. The citrus aspect is up for debate. Some people swear by lemon in their water, and others argue that it does more harm than good. What do you guys think?
I've never had any issues drinking something hot before performing. In fact it's one of my go-tos, especially if I've just been traveling or in some other less-than-ideal situation.