as my after-work fluid intake is mostly beer, I realized that now my brain cannot tell the difference between thirst and alcohol cravings.

Does your at-work brain confuse thirst with alcohol cravings too?

One idea would be thirst-like feeling -> drink water -> re-examine, but water is not a very good thirst quencher.

So test this by drinking something that isn't beer or water but matches your other criteria for good thirst quenchers. Carbonated water with lemon or lime juice in it will meet the criteria that you listed, but actually staying hydrated with water will just prevent you from getting thirsty in the first place. Seriously - ginger ale, lemon-lime or orange soda, etc.

I am toying with the idea to alternate alcoholic and non-alcoholic beer in the evenings to de-train the association

What? You're suggesting that you should train yourself to associate the taste of beer with satisfying your craving for hydration here, so the association that you're trying to de-train is the one between beer and satisfying alcohol cravings? That's crazy, dude. Look at how much energy you've put into thinking about ways to keep drinking beer while avoiding satisfying alcohol cravings and put the same amount into thinking about ways to not drink beer. That will be an easier way to decouple the satisfaction of your cravings for hydration alcohol.

I'm an alcoholic and have been sober for about 7 years now so take that into account. My advice is that you quickly try all the ways you can think of to control your drinking. Make notes about what you're trying and how well it works. Track stuff like servings of alcohol consumed, etc. so that you can look at how well your control mechanisms work. Spend some time with no control mechanism in place and just track your consumption for a baseline if necessary (maybe even do this for a week or two in between trials to see if your baseline fluctuates). Make notes about things that trigger cravings. If something works, tweak it or stick with it. If none of them work, consider that you'll either need to abstain entirely from alcohol (and avoid things that trigger cravings for a little while) or that you're just going to slide further into alcoholism and make the necessary adjustments in your life to do those things. Gather information and be honest with yourself.