Why doesn’t this exist?
Take dried beans, roast 'em, grind 'em, and brew some bean juice?
I have no idea if it would taste good or not, but we don’t know if we don’t try.
Edit: I need to see what dried beans I have and maybe go shopping. I will give this a try with a couple different types of beans and report back if I fart or not.
I drank it in Taiwan. It’s just one of many drinks made from ingredients we never thought of, like mushroom drinks and cereal grain drinks.
https://www.agv.com.tw/product-category/beverages/
Just wanted to add that tea with black beans, red beans, roasted barley, roasted rice etc are common in Japan. I assume Taiwan has the same, judging from the drinks posted above (the label even says the Japanese name in roman letters).
Barley tea is delicious.