Translation (I think): My brother is getting over a drinking problem. What are some suggestions for bad-tasting alcohol for him to carry around in an "airplane bottle" so that he will be reminded not to drink when he wants to?

This is a bad idea. He will just acquire a taste for whatever "tastes bad". This isn't going to be some magic trick that nobody has ever thought of.

I was lucky enough to be able to quit without any programs, but in my worst, I was choosing things that were "harder to drink" because of their taste (like the most bitter beers I could find) so that I would "drink slower". All it did was make me acquire a taste for really bitter beer and I drank as fast as ever.

I read that twice and I'm at a loss as to the meaning of most of it.

Nothing. That’s not how alcoholism works.

So your brother's solution to the drinking problem, is that every time he thinks of drinking alcohol, he drinks a little bit of alcohol? And by drinking a little bit of alcohol, it prevents him from drinking a lot of alcohol?

Tell him to get on Naltrexone if he wants to drink himself sober. Its legit and one of the most effective approaches known, actually retrains you so alcohol doesnt get you what you expect from it

Jepson's Malört. Famously bitter. I think it's nice, but it's often served on a dare in bars in the Chicago area.

Backup option would be straight Campari. He will need to be ok with probably dying his mouth red when he takes a sip. Mix 1:1 with some Fernet Branca to add some menthol and bitter herb flavors.

If he finds bitter flavors tasty then idk.

What in the hell is this word salad?

Are you having a stroke OP?

Bitrex and water

Akvavit

How about instead of gross alcohol, he punches himself in the balls when he wants to drink? He'll still get the Pavlovian response but without having to continue drinking.

Bitrex is a substance you put in poisonous stuff (like antifreeze) so that kids and animals don’t drink it.

https://www.bitrex.com/what-is-bitrex/

Underberg?! Or other incredibly bitter and foul liquid? It's a novel idea but I don't think it would really work. Maybe if you made it even more potent with sucrose octaacetate or denatonium benzoate (active ingredients in those nail varnishes that are supposed to stop you biting your nails).

Bitrex

Aviator gin?

Say what? Is this from grok?