Mod lists.
Fabric Loader 0.13.3
MC 1.18.1
Is it possible to fix it with a datapack, or do I have to wait for update?

Within .minecraft/config, or through Mod Menu you can toggle this on and off by yourself.

That legit is way too out of vanilla why defaulted to disabled? XD

unless I've disabled it. which would be my bad then

It's disabled by default because we've added milk bottles, and since there are both water bottle and water buckets and that you can't drink water buckets, it makes sense that you don't want to drink from milk buckets + you would drink 3 times a milk bottle.

That.. makes sense. I would've never found out about the bucket weren't because of Dehydrated though(It satiates dehydration the fastest)