Consider this from the point of view of integrating whole body metabolism.
The body operates on a fuel economy built around glucose. Active muscle produces lactate (C3) which is exported to the liver through the bloodstream. Liver converts lactate to glucose (C6) which is then exported to the tissues.
What if muscle produced ethanol (C2)? Liver metabolises this to acetate. This could be converted to acetyl CoA and so on to fatty acids, but there is no way to achieve net synthesis of glucose from acetate. Muscle can of course use fatty acids, so you could conceive of an alternative system based upon this. It may be that this is less efficent from the point of view of energy useage - I haven't checked this because there is a more compelling argument against using ethanol.
According to this paper, lactate levels in the bloodstream can reach 15 - 25 mM during exercise. If muscle exported ethanol instead of lactate then blood alcohol content (BAC) would reach the same levels.
The middle of that range, 20 mM ethanol, is equivalent to a BAC of 0.076% which is just below the legal limit for driving in the USA and the UK, and above the legal limit in many European countries. This BAC is associated with effects upon reasoning, depth perception and peripheral vision. So, from an evolutionary position it really wouldn't make sense to have a metabolic system based around sending this much ethanol through the blood.