Bean juice is a unique food in Beijing. When using milled mung beans as vermicelli or flour, the starch is taken out and the remaining light green and blue soup is fermented and boiled. It is said that as early as the Qianlong period, bean juice had been introduced to the royal family. There is a saying in old Beijing that you can't be a real Beijinger without drinking bean juice. Because the smell and taste of soybean milk are unique, it is difficult to get used to it unless it is exposed for a long time.

Drink bean juice is exquisite, first of all, it should be very hot, and occasionally a few bubbles are the best. Moreover, it must be served with finely cut shredded mustard, drenched with spicy oil, and at the same time, two "inby children" must be boarded. The main taste is sour, the aftertaste is sweet, and mustard is salty and spicy, accounting for four of the five flavors. Coupled with the crispness and fragrance of inby, it is a perfect match!