What sort of daily oral hygiene should my teen be engaging in?

Preferably toothbrushing after all meals is desirable, although this may be impractical after lunch at school. Dealing with the malodor of "bad breath" can be more challenging than simply using mouthwash, but the vast majority of the time, good dental hygiene with toothbrushing (preferably with an electric device), as well as good gum hygiene (which is oftentimes addressed by an electric toothbrush) are a start. Dental flossing is also helpful.

If this does not address the issue of "bad breath," then sinus infection and or intestinal problems have to be evaluated beginning with the pediatrician.