We say that a little of what you fancy does you good

Here are some practical tips:

Lubricate your voice – drink plenty of water
Coffee and tea will dehydrate you and not help your voice

Get plenty of rest if you know are going to have to exert yourself vocally
If your throat frequently hurts after a day at work see a doctor

Chocolate and dairy foods produce mucus which can clog up your voice
Spirits and hot or spicy food are not too good for it either