I have been dealing with my sourdough starter since about 1-2 months ago, when I started it from scratch with just water and flour .
In the last 2 refreshments I have added some honey, just 1 teaspoon each time to deliver some easy-to-digest sugar to my sourdough, I don't think it's too much based on the quantities of water and flour . The real difference is that in the past I have used a bowl covered with a wet piece of cloth, but since the last 2 refreshments I have been using a big cylindrical container made of glass with a plastic tap, and it's almost airtight, it's really different from just having a cloth on top of a container .
My sourdough starter was developing a really good smell, it was a "flat" odor of flour mixed to water in the first days, but it developed into something more fruity in the next days/weeks . Now in the new sealed container, stored at room temperature, away from direct sunlight, in the back of my cabinet, it started developing a punchy alcoholic smell .
I suppose that it was something I should expect from bacteria that goes into anaerobic mode, but my questions are about the cooking aspect of this :
If you've truly gone anaerobic and the smell is off, you are growing things other than the intended cultures...
As a rule, I simply feed mine flour and water. No sugar. The cultures can get along fine with the flour. (I did read in a reputable baking book about adding leftover water from boiling potatoes, for the starches, but I haven't had a chance to try.)
If the smell is off, I would dump and start over in a more breathable container. Your entire goal is to grow the sourdough cultures and let them flourish in their happy environment. And as you've smelled, there is a distinctive scent of happy sourdough. Now if the smell has changed, you lost your scented sourdough and are now growing something else.
I've kept sourdough for over a decade, and it's from a culture that is 84 years old. But if it smells funny (or gets brightly colored mold), he's going down the sink faster than dishwater. It's just the nature of the beast.
Most likely, the yeast in your starter are getting tired and/or hungry. A starter will start developing a strong alcohol smell and start "leaking" a dark fluid once the yeast start running out of food. This happens to me if I neglect my starter for over 2 weeks or so.
I would recommend keeping your starter in the refrigerator, not at room temperature. You only need to leave it at room temperature for about 6-8 hours after feeding (or until it starts rising and appears bubbly). Keeping it cold will slow down the yeast metabolism and keep it fresher longer.
I only feed my starter an equal mix of flour and water, and make sure to at least double the size of the starter (8 oz starter needs at least 4 oz flour and 4 oz water at feeding time). Flour provides all the nutrition your yeast need, and you want a yeast culture that is well adapted to eating flour instead of other sugars. This mostly comes from my homebrewing experience; a generation of yeast raised on pure sugar start losing the ability to properly ferment beer.
The alcohol was not a problem in my case.
I want to clarify that my sourdough was not producing any liquid in any visible quantity, the alcoholic smell started to fade as soon as I leaved the container opened for a about a day .
I have also used the very same sourdough, without refreshing it in the meantime, for my latest baked goods and it's active and kicking .
Alcohol is a natural product of yeast fermentation. That it is being produced is nothing, in and of itself, to be worried about. However, keep in mind that natural "products" of any biological process tend to be the waste products, and isn't that great for the producing organism to have it accumulate. Usually we notice it more when we've neglected our cultures and a good amount has accumulated.
Just pour it off before using or feeding, and if it seems like the quality of the starter culture is degrading, start a fresh one from scratch and inoculate it with your existing one.