Bad breath is usually worse:

• Upon awakening.
• When your mouth is dry (lots of things cause dry mouth - not drinking enough fluids, having just given a long speech, being under stress, hundreds of medications...)
• After indulging in products with high levels of proteins, such as milk products and meat. If a little piece of meat remains between you teeth for a time, it is rapidly putrefied. Coffee may increase malodor, although no scientific evidence is available. Foods containing onions, garlic, (cabbage?) and various spices may cause bad breath. Some of this odor may be due to the odorants being released into the lungs from the blood stream, sometimes for days following ingestion.
  Directly prior to or during the menstrual period, perhaps because the gums tend to get swollen and trap bacteria and/or debris.
• Bad breath is also related to alcohol, perhaps because it can dry out the mouth.
• If you don't floss regularly.
• If you have gum diseases, or have dental problems.
• A recent research we conducted shows correlation between bad breath and BMI (body mass index), which means that statistically, obese people are more likely to suffer from bad breath. Further research needs to be done to find out the reasons for this.