Like the thread says if possible no links cause i've read most of it.
Anyway I'm a kid which doesn't drink coffee first of all so i have 0 idea or knowing basically nothing about coffee. As far as i've read it seems simple just taking cold/old cup of coffee and watering the soil of the plant/nep.
One qiestion is when u say black coffee does it have to be the beans itself made into coffee(is that possible?) Or do i buy those ready made coffee powder without cream and sugar? If its the latter, i have another question, aren't these ready coffee powder mixed something else which might harm the plant or anything maybe oil or something ( i really don't know ) or they dont mix anything into the powder