

Where I live, they will often have a label on the pack that says whether it can be “divided” or not. I agree though that it’s a grey area until you see packs that have already been opened. For example, I wouldn’t take just one yoghurt, and I would never open up a pack that had glass bottles, so it seems unique to plastic and cans.
Depends a bit on context, but let’s assume you’re meeting someone new that’s being introduced to friend group (friend of friend).