Kinkan (金柑) is Japanese for kumquat. To the best of my understanding, the kumquat is valued primarily for its goofy name in English-speaking territories (and in particular by English-speaking improvisational comedians), but in Japan they are believed to have throat-soothing powers.

But how to activate these powers? In our household, like this:

1. Pull the stems off some kumquats and place them in a saucepan.
2. Poke holes in them so that they don't burst.
3. Cover with water and simmer over a low flame until they turn transparent.
4. Add some sugar -- say, a little more than half as much sugar as there is kumquat in the saucepan (by weight).
5. Keep simmering until the water turns into sugary goo as well.

We are aiming here not to candy the kumquats, but rather to create a syrupy amber hell through which they drift like bloated, awkward ghosts. This we will take into ourselves.

It is best when blended with kettle-hot water, so what you will usually want to do is tip a kumquat and a little syrup into a cup, tear the kumquat apart with a fork or similar, and then pour the water over the top. The same kumquat is usually good for a refill or two, although you may want to add more syrup.

I do not know if the kumquat is actually good for sore throats or if any hot, sugary drink would do as well, but I can confirm that a few cups of this can at least calm the virus down long enough for you to get to sleep.