If you just want to drink bean juice, you can find it in many places, but the most authentic one is Jinfang Bean Juice Store, which used to be in Ciqikou. Later, Chen Yi moved to Hongqiao, and later moved to the North Gate of the Temple of Heaven, just at the northeast corner of the T-junction. It is easy to find.
In Beijing, time-honored snack bars all sell bean juice, such as Bai Kui Laohao in Kuanjie, Long Fu Temple Snack Bar, Baita Temple Snack Bar, Nanlaishun Snack Bar (southwest corner of Grand View Garden) and so on.