There's these toothpaste tablets/pills, which you put into your mouth, bite on them and then they turn into toothpaste for brushing.
When I first saw those, I also thought, they'd somehow clean your teeth without brushing. Like, maybe they're one of those fizzy tablets, which I believe exist for cleaning fake dentures. Or when I then read that you bite on them, I thought, maybe they're like special chewing gum. But yeah, it's just toothpaste without the water.
Yeah, I was trying to find something that didn't need water for when I'm away from a sink. Saw those tablets and thought they'd be great! Luckily I read the description.