sweetener
US /ˈswiːt.nɚ/
UK /ˈswiːt.nɚ/

1.
a substance used to sweeten food or drink
:
•
Many diet sodas use artificial sweeteners instead of sugar.
•
Honey is a natural sweetener.
2.
something offered to make a deal or situation more attractive
:
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The company offered a bonus as a sweetener to close the deal.
•
The new features were a great sweetener for the software package.