Have you heard Joe Cocker? LOL

There are a few things to consider when answering this question.



The quality of your singing voice is directly related to the overall health of your body. If you are drinking enough to cause your overall health to deteriorate, then you are causing your voice to deteriorate as well.



However, even if you are not drinking enough to damage your health, you can still cause damage to your voice. This is true even if you do not drink enough to "feel it".



Alcohol (even just one drink) numbs your throat. This can indirectly cause damage to your voice since you need the nerves in your throat to send signals to your brain.



For example, I might have accepted a gig singing in a night club, and I am quite nervous and have a stiff drink before I go on stage. Normally, when I have not had a drink, I know when my voice is tired or when I have pushed my voice too far because I will feel discomfort in my throat. But tonight, since I've been drinking, my throat is numb. I push my voice past its usual boundaries (this may take the form of singing too loud, too high, too low, or simply for too long a time period) and I do not receive those warning signs. So I keep going, and I have just caused damage to my voice.



Now if this situation happened just once my voice will recover. But if it were to happen often, there would likely be long term damage.



The occasional drink, when you are not singing, followed by enough water to counteract any dehydration, is very unlikely to cause any damage.

Alcohol is a dessicant: it replaces water in your body and dehydrates you. Note that this is why you urinate so much when you drink alcohol. Also not that that you urinate clear, a normal indication that your body is well hydrated. In actuality, this is happening because that alcohol is forcing the water out of your body.

Anything that dehydrates you is, in an objective sense, bad for your voice, as the mucous membrane tissues which make up your vocal mechanism are approximately 90% water. The protective layer of mucous they secrete is nearly 100% water. So, if these delicate tissues become dehydrated, they stop secreting mucous, and are more subject to stress and injury. Some voice teachers will advice avoiding alcohol completely because of this. However, alcohol in moderation, accompanied by enough water to maintain good hydration (a singer should alswyas get enough water to maintain good hydration, anyway).

My usual recommendation, based on experience, is one 8-ounce glass of water per serving of alcohol. Note that, whatever the alcoholic beverage, a 1.5-ounce serving of hard liquor at 40% alcohol, a 6-ounce serving of wine at 10% alcohol, or a 16-ounce serving of beer at 3.75% alcohol (these numbers are approximate; serving sizes and alcohol contents will vary, but within acceptable limits), all contain the same amount of alcohol (.6 of an ounce), so the same amount of water will counteract their dessicant effects. If you are observant, you will find the amount of water that works for you.

Dehydration is one of the main contributors to hangovers, too, so getting enough water will mitigate those as well. Now, this answer doesn't address the immediate effects of alcohol on control of the voice. Singing drunk is a problem for the same sorts of reasons as driving drunk (though fewer people get killed). Your judgement and attentiveness are impaired. You are more likely to oversing and less likely to think about proper technique. Once in a while, this will not be a problem, as your body will have the opportunity to heal from any damage you may do. Do this too much, though, and you will find the damage compounded.

So remember the key: MODERATION.

What alcohol actually does is it makes you lose control of your voice. Instead of singing a steady tone, you would wobble all over the place. Plus, it dries your throat out.

Hear! hear!, Hemiman. nor Sinatra, nor Willie Nelson, etc &c.

It did not seem to affect Dean Martin any.

Personally, I don't seem to notice any changes in my singing voice whenever I drink alcohol. But you would probably hurt yours if you would take cold drinks too offen, but not alcohol in particular.