Imagine this thing growling menacingly at you if it saw you littering... on some people, that would work better than a fine.

Even better, following you around for a while, still growling.

cigarettes should have serial numbers written on them, tied to the drug addict in question at the counter: this user is purchasing this serial number. Cleaning services could easily report any drug evidence and report it to the authorities

I don't think that would work.

I've thought about this when I see bottles and other crap strewn on the streets or in parks.

Then I see a garbage can nearby that's been tipped over by someone, or an animal, or the wind.

A cigarette butt or bottle on the ground doesn't mean the person who bought it and used it tossed it on the ground. It could mean they put it in the designated garbage and someone came along and strew garbage everywhere.

German citizens who bring back Plastic bottles to supermarkets receive 0,25 € for each one. Fields are pristine needless to say

Meanwhile in The Netherlands, the homeless dig through trashcans for their €0.15 bottle deposit and leave all the trash next on the ground.