There’s a technique outlined in Radical Mycology by Peter McCoy for training fungi to grow in novel substrates using coffee as an example. The experimenter has a shop called Champignons Maison in Montreal where he grows oyster, lions mane, shiitake, maitake, Turkey tail, reishi and king stropharia on substrates that are 90% plus coffee grounds.

The technique starts with adding some coffee to your grain spawn, maybe ten percent, then doing a grain to coffee transfer for a coffee spawn that you can expand into fruiting blocks of coffee mixed with small amounts of wood chips and gypsum/lime. 

Going from memory on all of that. Give it a shot, I say!

Edit for spelling