One potential cause of the bad taste in your mouth when you wake up in the morning is gastroesophageal reflux disease (GERD), a condition in which acid produced in the stomach refluxes up into the esophagus. This problem can also cause heartburn, and is often triggered by certain items such as spicy food and alcohol. Morning symptoms tend to be more pronounced in individuals who consume late night snacks or meals. Avoiding eating late and elevating the head of the bed or sleeping on more than one pillow can often alleviate these symptoms. Your primary care doctor
can help determine if this is the cause of your symptoms, and can prescribe medications to reduce your stomach acid production if lifestyle modifications don't provide enough relief.
Your sinus congestion could also be a potential cause of your symptoms. Drainage of the sinuses into the nose can lead to mucous collection in the back of the throat, some of which could enter the mouth and be perceived as a bad taste. Treating your sinus symptoms with medications such as nasal and oral decongestants and nasal saline sprays may help to reduce your symptoms and leave you without an unpleasant taste in your mouth.