I was recently given a used Keurig from a relative. Unfortunately this person was a heavy smoker. I ran vinegar through the machine as well as removed and rinsed the little cup that holds the k-cups, but it still smells and tastes like tobacco. What can I do?
First of all, note that the smell of the machine itself is unlikely to come from the interior of the parts that heat and transport water -- after all, they are regularly cleaned with hot water and smoke has a hard time getting there.
So running vinegar through the machine won't change that. Rather, it is the other surfaces that cause problems. Thoroughly cleaning all surfaces of the machine may help a little bit (including the easily accessible ones behind the cover), and storing it in a room that is thoroughly aired for some months should also help to some extent. Depending on the temperature, a garage may also be an option. You need to be careful to not break the machine during cleaning and airing, though.
Pass it to your local authority's electrical recycling scheme, then purchase a new one.