I can’t imagine buying caffeine for its own sake. The effects aren’t good enough. If I didn’t drink coffee/tea I just wouldn’t get any caffeine.
Also as I understand: it is against the rules to import it so it will be stopped if caught but not against the rules to have it so you do not get fines or anything on record. Thus if you buy it abroad you can bring it into country with you unless caught in which case they confiscate it. This used to be the same case with Modafinil / Adrafinil and I suppose it is still the same.
I don’t know what I would even do with liquid caffeine. But again, I don’t want caffeine badly enough to be looking for alternative ways to get it.
The problem of course is that they want to make sure you don't take too much caffeine and have a problem, so they want to limit the strength of what you can get and my understanding from him was the strength was limited so that it was hard to get anything into you with the strength of a cup of espresso, as ridiculous as that sounds but nanny-statism is a thing.