Excess sugar or glucos in the body draws water from tissues and causes the problems associated with diabetes. Excessive thirst can often indicate that a person may be diabetic.Water helps break down sugar naturally in the body and is one of the best treatments in diabetes, Dehydrated tissues are bad.Water is the essential product that helps the cells to function properly. It also helps prevent fatigue and improve physical performance. Yes it can interfere in blood tests in diabetes and persons should be well hydrated prior to testing. In the elderly, a coma may be brought about by dehydration.