I've watered indoor plants with tea but never coffee. I can't see where it would hurt, though.

I had to smile at your coffee question. For years I kept my houseplants in my classroom alive watering them with coffee. The schoolboard had a rule against teachers drinking coffee with students present, so on my break I'd make the trek involving three flights of stairs and a connecting hallway to the part of the building that had water. I'd get coffee, then work at my desk until my class returned, set my coffee aside, and at my next break empty my now-cold half cup of coffee into a flowerpot. The plants thrived, so I quit carrying water seperately for them, and just "coffeed" them. I now habitually pour leftover coffee over any plant in sight...even the plants at roadside rests. :o)

My mom has an ivy that starts to die off if she doesn't feed it tea once a week or so. Now, they have a water softener in their house and she was told the tea helps keep the soils more acidic which is why plants like it... Not sure if that is right or not, but I have some plants that love coffee and some that don't. All my plants are in the house as we are in an apartment building. I am assuming that being in pots thy are more sensitive to the things you 'feed' them rather than ones planted directly in soils, like roses and shrubs :)