With tea there are a couple things. First, never drink tea thats piping hot. This isn't good for your voice. It can bring the blood to the surface of the throat aka some swelling, not really noticable to you until it makes it harder to sing. So just drink hot tea thats not THAT hot. Second, don't drink caffienated tea. Caffiene will dehydrate you which then makes it worthless to be drinking your glass of tea to hydrate you. So always drink decaff. Lastly about adding things, I mean it's really up to you, if your voice was under strain I would stay steer clear of anything that could diminsh it, but if your fine then adding a small about of sugar to your tea probably won't hurt you.
After your done with your tea...have a nice tall class of cool water...STAY HYDRADED!! lol it's the way to go
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