In my opinion in forests or nature parks everyone has the responsibility to behave respectful towards nature. This means do not even cause rubbish. If someone wants to sell stuff, then do not sell disposables. Instead serv in glasses or similar. On the other hand people should not buy disposables in nature parks. Just bring your own stuff e.g. thermos flask.
Just take your own rubbish home
Why are they doing this? What do these people need so badly that they think this is a good idea?