What could be wrong with a doberman not eating and vomiting for 5 days?

Our 11 year old Doberman as not eaten or been able to keep down what little he has eaten in over 4 days. The water that he was drinking up until last night was not staying down either. He is now refusing water. He was offered chicken and rice and when he smelled it, he vomited. The vomit over the last day has been very frequent (up to 2x per hour) and it is bright yellow (bile) to dark brown and very bad smelling. His dietary issues and severe weightloss has been the most concerning however, his right eye also has green/yellow discharge that we are worried about. We will be taking him to a veterinarian but would like guidance/feedback on what to expect at that visit as well as what to do with him in the mean time.