Our kids would always throw their rubish on the seat next to them, on the floor of the car, or try to hand it back to us, so I designed a bin / trash can to perfectly fit into the cupholders in our car, which they can easily reach and use.
It was designed intentionally with an open top to make it as easy as possible for them to use / to fit larger items (spin lids essentially halve the opening). I also made the top portion (clear of the cup holder taper out to make the opening larger / to fit more in. The open top makes it easier for us to empty / clean.
I have included both my print file which perfectly fits a Nissan Pathfinder R52 (2016) down to the tapered cup holder shape, as well as the simple fusion 360 model so anyone can edit themselves for their own car. It is just a simple revolve with a shell, so even basic users will be able to update with their own dimensions by editing the one sketch.
Enjoy the clear car!