Then it was pretty foolish of you to just say "I can't." with no elaboration when the waiter asked about telling by taste. Well, either foolish or a deliberate bait so you could berate him more easily. Neither option looks good.
If you wouldn't have answered like that, then the story isn't about you.
It's a joke, and not a serious dialog, exactly because there may be a difference (not necessarily life and death, but maybe the price), but it fades beside the fact that the drink is so bad that its taste is incomprehensible.