When I visited amsterdam I saw little or no trash. After watching a while, I noticed they have guys with little witches brooms cleaning everywhere (it was really interesting to watch, turns out they used to use more modern ones but they don't work as well), followed by street cleaners. The little brooms made all the difference, ferreting out all the half-cloaked garbage dropped by tourists. Seems completely routine and normal and not authoritarian.
In my experience a clean public space tends to stay clean even without outside input, while trash leads to more trash. Apparently people feel more guilty for making a clean place dirty than for making a dirty place a bit dirtier.
Thus a good way to fix trash on the streets is to pay people to clean it up, and after a short while you can get clean streets with a very moderate level of cleaning effort.