Take a look at what you’re putting IN your mouth.
It’s no secret that garlic and onions make for less than ideal breath, but if you notice it has taken a turn for the bad, take a look at your diet. Have you significantly changed what you’ve been eating? Even minor changes in your diet can cause a bad taste, as well as bad odor, in your mouth. And are you hydrating properly? Dehydration can lead to dry mouth, causing bad breath as well (just one more reason to drink the recommend eight glasses a day).