Really, mint doesn't play well with others. Especially not spearmint! Peppermint, it's okay, since it gets to represent a major holiday it seems to have a better attitude towards other foods, but for the most part, mints are terrible terrible flavor collaborators.
My point is, I really think that more people would brush their teeth upon waking if it wasn't going to make drinking their morning orange juice into an experience of taste torture.
The problem is to find a flavor that is palatable with most things, doesn't leave a terrible aftertaste, and isn't so bizarre as to turn the consumer off to buying it.
My first thought, as it usually is, was BACON! It is the perfect flavor, but alas, probably not going to make for the freshest breath. Gonna need to go with something sweet. Then I thought waffles, mmm buttery syrupy waffles. Might be a hard flavor to recreate.
Perhaps the solution is orange juice flavored toothpaste. And none of this "orange mint" that was tried, that just makes the prospect of toothbrushing, itself, torturous. I mean, people like orange juice, right? It is refreshing, delicious, and full of vitamin C. I'd be willing to try it.
Perhaps a line of drink flavored toothpastes would be best for all day brushing. Orange juice, lemonade, merlot wine, vodka...