I put a big ziplock bag full of those "disposable toothbrush" things in my car. Basically a plastic toothbrush that has a little toothpaste you can swallow.

It's not a real solution; but I find I at least use them. I usually leave the house and remember in the car "fuck I didn't brush my teeth again". So I use a disposable one and just brush while I drive.

They aren't a replacement for actually using a toothbrush and toothpaste. But, at least when my brain refuses to go brush my teeth I at least get something scrubbing them in some way.

It basically gives me a scenario in which I have no excuse not to use it. Because I'm already going out and I didn't brush my teeth.

Not really a solution to your main issue. But, sometimes the solution is just changing things to work for whatever your brain has issues with and trick it into a scenario it can't rationalize out of.