10. Green Tea http://custom.amanaimages.com/allabout/ImageInfo.do?refer=imageid&imageid=10341009153&d=1453296757451 You should really drink green tea as much as possible for prevention of colds anyway, but it’s even more important when you’re already sick. It's full of antioxidants and it helps your metabolism, but most of all it can kill harmful bacteria of all kinds, keeping you young, skinny and healthy. Green tea is sold everywhere in Japan in different kinds, qualities and price ranges, so hop to your local supermarket and check the 緑茶 (ryokucha) section (and read the Wikipedia entry to distinguish among all the different kinds).