I have some ideas for this issue. Those are;
-When you wake up, then you go to the kitchen to pick some salt before going to clean your teeth.
Next you put it in your mouth and wait about a minute.
-Second way is so easy that is to pick some chars form your kitchen as well.
Then you mash it and take it with you to the bathroom.
Next put it in your mouth and wait about a minute.
These two way can make your teeth whiter.
Nutthaphol 044 4EN