I remember when I was a kid and was having a cold and fever my mom always gave me homemade raw uncooked sauerkraut and also a glass of sauerkraut juice (the sour water squeezed from the sauerkraut). It's supposed to be loaded with vitamin C and other good stuff to strengthen your immune system especially during winter months and it was also great fever reducer. I don't know about the vitamins, that's just what my mom always told me but I know it worked pretty well. I loved the taste of it so many times I was just snacking on it or drinking the juice because it was also a great craving quencher.
Oh, I also remember it was great for hangovers when I was older.
The side effect of sauerkraut is it gives you gas.
Sauerkraut is big in Czech Republic so most of the families used to have a big jar of their own homemade sauerkraut at home. We always had our own in our cellar. I don't think people still do it there because I assume it's easier to buy it now.