How to get my boyfriend to brush his teeth!

I know this is gross. My boyfriend brushes his teeth maybe 2-3 times a week! I get on him all the time about brushing his teeth every day. He always just says, "what's the point if I'm going to go drink a mt. Dew?" Cool babe, I get that. But how many mt dews did you drink yesterday? Did you brush your teeth before bed? All of that sh** is still on your teeth from yesterday! I don't get it! I HAVE to brush my teeth as soon as I wake up. Wake up, pee, wash hands, brush teeth. I don't brush them after every meal.. but I do 2 times a day. It's so gross! I don't know what to do to get him to brush! I feel like I'm treating him like a child!