Brewer's spent grain is a waste product from breweries. It can be used for various purposes, including using it as an organic material in making the bokashi sprinkle.
If the spent grain is relatively fresh (less than a day old), then it could be used as is, without drying, since the microbes should be similar to or compatible with the bokashi microbes (the EM) during the bokashi fermentation process. Otherwise, it would have to be dried in order to avoid possible proliferation of incompatible microbes while the spent grain is left moist for a long enough time unused—depending of ambient conditions (temperature, humidity, and airborne particulates). After drying (e.g., air-drying for several days), the spent grain can be used in making bokashi similar to the ratio of ingredients as with making wheat bran bokashi.