Informal Something added as a further inducement or incentive.(noun)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "sweetener" in a sentence
"The sweetener is that the first 500 people to book tickets using their Twitter ID would be able to redeem a 50% discount (still valid as of 2pm EDT, 20 Feb)."
"It's obviously true that the small amount of lactose in a single packet of sweetener is probably not an issue for most people with lactose intolerance, just as the amount of lactose in a single pill is not an issue."
"Palatinit claims its sweetener is the only low-glycaemic carbohydrate that supplies energy in the form of glucose over a prolonged period of time."