Soybean juice is a special flavor that old Beijingers love very much, and it is also a must-try snack when traveling in Beijing. It is fermented from the leftover soup made from water-milled mung bean products. It has a special smell and a sour taste in the mouth. Most people may find it unacceptable when they first come into contact with it, but many authentic old Beijingers are very obsessed with it. Drink a few sips of soybean juice with Jiaohuan for breakfast, and feel refreshed.