Hello and welcome to healthcare magic community . I will be very happy to help you . Well ! Drinking is associated with some problems of the stomach and chronic drinking with liver too . If you had such an issue before too and same black substance came out , you should see a gastroenterologist in order to rule out any ulceration in the stomach etc. However , you should keep in mind that anything eaten up together with drinking having dark color might come out too , as a result of excessive drinking . If such a patient came to my clinic with such signs I would rather send him / her to gastroenterologist for complete check up . Hope I have answered your question and please never hesitate to ask follow up questions if you have anything to ask further .