How does fractional distillation separate out ethanol and water?
It does it very imperfectly........
Both ethanol and water are infinitely miscible, and both have very similar boiling points.
It follows that when we distil wine, to make brandy for instance, the distillate contains a lot of water. Ethanol or methanol as used in the laboratory as pure, anhydrous solvents takes a lot of work and care to prepare properly, and when you expose it to the atmosphere, you can actually see the volume of the liquid rise as it drinks up atmospheric moisture.
See this old answer.