Sweeten up phrase
To cause food or drinks to have a sweeter taste by adding sugar, etc.
After sweetening the sauce up, I tasted it again.
I used condensed milk to sweeten up the smoothie.
To make someone friendlier or happier.
She sweetened her son up with a new toy, but he got fed with it pretty soon.
I know that he was just trying to sweeten me up to borrow my car.
= sweeten (up) the kitty.
The verb "sweeten" must be conjugated according to its tense.
The origin of this phrase is not clear.
To be thankful or grateful for one's good luck usually while avoiding a bad situation
You should count your lucky stars as you managed to avoid that violent car accident.