My friend seems he is catching a cold. He sounds like he is losing his voice.
Some people know tea with ginger is good for your throat.
What do you do when you feel like you are getting sick?
In Japan, we drink tamago-zake.
Basically it is sake mixed with a raw egg.
It has to be a very fresh egg, of course. The eggs in Japan are freshly laid and people eat them raw all the time.
Here is a recipe. If you ever go visit Japan, you can try this.
1) Warm sake.
2) Put row egg and sugar in a bowl and mix them well.
3) Strain it to make it smooth.
4) Pour sake into egg little by little as stirring it.
5) You can add little ginger or use honey instead of sugar.