Verb. To throw something extra-cool in the already-existing good deal, making more appealing.

It's something like what a car-dealer does when offering a vehicle with extra comforts... but the items in question are for free.

Deal sweeteners work for those who are truly smooth talkers, and those blessed with a silver tongue who
know how to talk a good deal. The difference is: Those kind of folks DO SO MORE than those who BS.

But beware... liars can do it, too, especially in working out a scam.