I have a couple of suggestions, I am not a mother of a 14 year old, but I was 14 a short while ago and have a brother who acted similarly to your son.
Have you tried giving him consequences for his actions? Like if he doesnt turn in his homework, he cant play video games or whatever he likes to do. Or if he gets an allowance, tell him if he losses another inhaler its going to come from his allowance money.
Or have you tried a reward system? You could reward him with something if he goes a month without losing an inhaler or remembers to shower everyday, maybe take him to his favorite place or get him the thing he has been wanting. So it will teach him if he wants something he will have to work for it.
I hope these suggestions are helpful. Good luck! I am hoping my 15 month old never grows up!