Thanks for posting your query,
yellow coating on the tongue can be the result of various factors: smoking, certain antibiotics, minor infections, diet, jaundice
(usually with yellowing of eyes and skin), thyroid
issues, spleen and/or liver anomalies, glandular fever
Brush and rinse thoroughly before bed.
Take a multivitamin
Avoid drinking beer or alcohol in large quanities before going to bed.
Drink a lot of water, even when you are not thirsty
I hope this information has been both informative and helpful