When i wake up in the morning i have a very acid taste in my mouth, once i do my teeth and a drink it goes. why does this happen?

Lots of reasons: Could be from acid reflux, hiatal hernia, not cleaning between teeth (Flossing) daily, improper brushing, gum disease, cavities, bacteria built up on teeth because of missed Dental appointments, food allergy, food selection, timing of your last meal or drink, brand of toothpaste. Sounds like your body is telling you to discuss this with BOTH your General Dentist and your Primary Care Physician.

Morning Mouth: During the night the salivary flow decreases, and if you are sleeping with your mouth open or if you have nasal or sinus congestion the mouth breathing at night exacerbates this effect. Low saliva flow allows the plaque acids to concentrate.