A bag of decent coffee and a set of refillable capsules...
coffee
Everything Coffee (including latte).
That might actually work. Just need to figure out if the machine they are using got refillable caps...
I got refillable Tassimo pods after the price of them shot up. It works fairly well now that I can easily add any brand coffee and get to feel good about using less single use plastic.
That sounds excellent, I'll definitely give it a try!
Depending on what pods they use, you could also look into "fancy" pods - Colonna has a Gesha pod (https://colonnacoffee.com/products/40-gesha-lungo-capsules-stockshare?variant=40477665296469). No idea personally if it's any good, though I have the pods here myself but the wrong machine 😅
Maybe Cascara?
Huh, interesting idea. Didn't think of that at all, I like it!
Never tried it myself, but sounded like a fresh idea with the restrictions.
I actually have tried it in Vietnam, and it's delicious. Just totally didn't cross my mind.