sweetener vs come-on

sweetener and come-on both are nouns.

Word	Noun	Adjective	Verb	Adverb
sweetener	Yes	No	No	No
come-on	Yes	No	No	No

As nouns, sweetener and come-on are synonyms defined as:

Other synonyms of sweetener include bait, hook, lure.

sweetener (noun)	come-on (noun)
anything that serves as an enticement	qualities that attract by seeming to promise some kind of reward
something added to foods to make them taste sweeter	anything that serves as an enticement