Ask neighbourhood drunks to buy it for you. Every neighbourhood has such a store, and drinkers tend to be a friendly type ready to help each other. Easy!
How to identify such a store? It will have to be a small owner-run establishment. Shabby if now somewhat dirty. A good sign is a cat on the counter because there is a rule against cats on the counter, and one small rule broken means greater transgressions are possible. The older the seller the better. Men are preferable to women. “Ethnics” are better than Russians who often have profound internalized fear regardless of whether there is any real danger. If a 24 hour store has booze and a standard selection of snacks it obviously stays open because of alcohol. But they usually won’t sell to someone they don’t know. Just identify such a store and wait outside but of course out of store keeper’s sight till someone walks out with beer or vodka. Ask them to buy a bottle on your behalf. If you ask an old school Russian you will get a 100% positive response.
Look at the situation from the seller’s point of view, and approach the great goal of alcohol procurement after 11pm in a manner that does not expose the seller, and you’ll get what your heart desires.
There are of course formal and official ways of getting a bottle. But these require calling and planning, which is my view goes against the very essence of drinking. “Sober driver” services will often deliver stuff. There are report of virtual cafes that operate same way as virtual addresses for the purposes of “visa registration” (talk to me if you need one). But if you need just a couple of damn beers these services make no sense.
There used to be a store in my neighbourhood that allowed clients to “steal” bottles. A neat trick too but you need to do it right. The solution we stumbled into yesterday seems by far the simplest and easiest. And a great way to “integrate” for you travellers.