Pure alcohol has no water. You will die within days without water.
For vodka, which has a high proportion of alcohol, you will put extreme stress on your kidneys to sort the alcohol from the water. You probably can't keep down enough alcohol to get sufficient water to survive. If you can, you'll wish you didn't. You will be in agony as your body goes into ketosis and you will be intolerably thirsty. You probably won't last long enough for vitamin C deficiency to set in, but if you made it that long, you'd literally begin to fall apart. Eventually you'd simply bleed to death.
