Point out to him that you had to drink it quickly because it was too horrible to savour, and that if he keeps buying it, cheap sit is, it will cost more in the log run because you have to swallow it fast so that you can't taste it.
Tell him it would be better to spend four/ five times as much on a decent bottle that you will sip slowly and swirl around your tastebuds, appreciating every delicious droplet and allowing your tongue to rest between each delightful sip.
And that not only will it ultimately be less expensive (we're playing the long game here, remember), but that he won't have a wife with breath that you daren't allow near a naked flame, and a headache that means she can only be carefully approved from behind a riot shield, and probably with a chair and a whip.