Volunteer for one day. Making a difference during your holiday is not so easy. But, with the local trash hunting events of Trash Hero you can easily join a beach clean-up or nature clean-up just for one day and make a part of your tourist destination better. It is a great way to meet local people and leave your holiday destination cleaner than when you arrived. No costs are involved, no experience needed and no further obligations. When you travel to Indonesia, Thailand, Myanmar, Malaysia, Vietnam, Singapore, Switzerland, Czech Republic, Poland, Romania, Serbia, Georgia, Germany, Netherlands, Kuwait, Cambodia or Japan there are active volunteer groups of Trash Hero that regularly/weekly host clean-up events. The best way to check upcoming events is on the specific Facebook pages that the local chapters host.
Note: they also offer options for online volunteering - to promote their worldwide activities from your living room.