If an otherwise active person on getting up can not hold a glass of water he ought to be taken to Emergency Room. Where a detailed physical examination, neurology and cardiology examination and investigations like serum electrolytes, renal function tests and EKG will tell us whether he has ischemic attack of brain or it is metabolic problems leading to such state. He needs to seen by a doctor and it is his job whether he/she needs any consultation with cardiologist or neurologist
I hope I made the urgency of the situation clear.
With Best Wishes.
Dr Anil Grover