you may be having gerd - gastro-esophageal reflux disease. what you may be tasting is regurgitated stomach acid and whatever you had to eat or drink before going to bed. this problem can be treated but you must first be properly diagnosed. there are over-the-counter medicines that can block some of this acid reflux that you can try. your pharmacist can help you select an appropriate medication until you can see your medical provider.
sometimes i wake up at night unable to breathe with a nasty taste of bile and it takes a minute before i can breathe