Hello I appreciate your concern blackish and stringy puke is suggestive of bleeding in oesophagous either due to liver disease or Peptic ulcer and a throat or oesophagus disorder I would advise you to consult your doctor for baseline investigation to assess the amount of blood loss by doing blood for hemoglobin and CBC and an endoscopy if need be. meanwhile try to avoid constipation by taking liquid paraffin like stool softeners Have dietary fiber to increase bulk of the stool. have lots of fresh fruits and steamed vegetables Avoid fatty fried junk and cold food or carbonated drinks. Avoid smoking and alcohol it could be dangerous for you maintain good hygiene Hope this answers your question Wish you good health