Body odor can be a real social problem for kids, and lack of hygeine isn't particularly healthy, either. That makes staying clean a "whatever works" situation, and gives you permission to use bribery to make it happen.
The payoff doesn't have to be huge: Points on a behavior chart. Relief from a disliked chore. Extra TV or computer time. A song from iTunes (my own bribe of choice for my music-loving kiddos). Anything that is highly desirable to your teen may provide the necessary incentive to follow through on the loathsome act of washing and deodorizing.
It may seem wrong to reward someone for doing what any responsible grown-up would do. And one day, sure, you hope your young person will embrace cleanliness for cleanliness's sake. In the meantime, though, there's no reason you should have to smell that, and no reason your teen should suffer the stigma of being obliviously oderiferous.
