Plus side is he smells all minty when he wakes up, and Dean always makes sure the tins in a safe place while Sam sleeps away the car ride.
Sam HATES the mint smell. Dean thinks it’s absolutely adorable, but Sam uses scented floss enough that he’s grown to hate smelling like it. And even though Sam usually ends up on the shoulder anyway, the tin is nice when Sam isn’t particularly happy with Dean.
The tin is better than being stuck in Dean’s pocket when he takes a nap and he’s annoyed with Dean. Everyone needs some space from time to time and these two don’t get much most of the time