I have diabetes and I have to force myself to drink enough water. If blood sugar is kept in a desirable range (through diet, exercise, and/or insulin and meds), excessive thirst is not a problem. At least that's my experience. The subject of this thread undoubtedly had high blood sugar.
Oh yeah, I am a diabetic too. I believed I caused it by drinking a 2 litre of Coke/ Pepsi per day for many years.
When my blood sugar was out of control, before I officially knew I was a diabetic, I drank 2 litres of soda per day + a gallon of milk every single day, and I was still thirsty.
ALl that ended with me in the hospital for 5 days with hyperglycemia. Almost died from naseua of all things. Heart attack came six months after that.
Fun stuff.
Now I have my diabetes on maximum security lock down, blood sugar is perfect every day, heart is in tip top shape, and I am in good physical shape myself.
Hopefully those troubles are behind me forever, and I also wish you much luck and skill in managing yours.