sweeten someone up
to make someone more pleasant. I had hoped that a week in the Caribbean would sweeten him up. The trip sweetened him up, but not for long.
sweeten something up
to make something taste sweeter. Where is the sugar? I need to sweeten this up a little. A little sugar will sweeten up the coffee.
1. To make something sweet or sweeter: The recipe instructs to sweeten up the sauce with a tablespoon of sugar. I usually add some honey to my tea to sweeten it up.
2. To make some offer more appealing: The phone company sweetened up their deal by throwing in a free phone. If you're still unimpressed with our proposal, we can sweeten it up with a great benefits package.