1.Coffee can cause xerostomia, more commonly known as “dry mouth.” That’s because coffee contains caffeine — up to 200 milligrams in a single 8-ounce or 237-milliliter cup — one of the chief culprits of decreased saliva and, in turn, a dry mouth.
Plus, a lack of saliva can make it difficult to wash away and digest particles of food clinging to the tongue or teeth, and it can even promote tooth decay
2.The other cause behind coffee breath isn’t actually your coffee. It’s what you put in it. Loading up a cup of coffee with cream, milk or even artificially flavored non-dairy creamer fuels the overgrowth of bacteria in your mouth. Stirring in sugar, an ingredient on which bacteria thrive, will put bacteria into overdrive. To make matters worse, coffee is highly acidic, yet another condition that causes bacteria to reproduce with alarming efficiency.
One solution to help combat coffee breath is to drink a watered-down cup of coffee without added cream or sugar. As unappealing as this may sound, it could mean the difference between stinky or manageable breath. Another idea is to switch to tea. Still hot and caffeinated (up 70 milligrams per serving), tea is far less acidic than coffee and won’t cause the same bad-mouth odors. If you just can’t manage to give up your cup of joe, chase it with a glass of water to encourage saliva production and, if possible, try slipping away to use a minty mouthwash!