Assuming that's true, I'd say estus doesn't hold many of the same properties as most liquids. For starters, it's very light and airy. If estus were to be poored out, it wouldn't douse like a normal liquid, but would dissipate instead. It's also not cold, but rather has a calming, constant warmth about it.
As for taste, it is very smooth, but with a light, bitter or ashy taste about it. Upon bringing estus into your body, it flows to your core and smolders like an ember, bringing with it not only healing properties, but also uplifting the soul and purging negativity from the mind.
So it's vodka. --- Magikoopa Security Force: Defend against the Shy Guys! Check out the demo (offsite): http://www.mfgg.net/index.php?act=resdb¶m=02&c=2&id=29243
Imagine if it was alcoholic. There could be an easter egg where chugging all 20 charges in a row and dual-wielding fist weapons gave your character the secret drunken boxing moveset. --- Sarcasm is sooo hard to convey in a written format.