Depends on how long I have. If it’s a workday and I don’t have much time then I brush my teeth first, if it’s the weekend and I’m not in a rush I eat breakfast first. I just do this on some idea that sugar (such as in milk) makes your teeth a little softer temporarily and you shouldn’t brush when they’re like that. That from what they say about brushing your teeth after coke but it stuck in my head.