keep someone sweet
keep (one) sweet
To do nice things for one in order to maintain their loyalty or to elicit some benefit from them in the future. She isn't the easiest person in the world to work for, but she keeps us sweet with a big fat bonus at the end of the year. He's been keeping the superintendent sweet so that he'll get a favorable review at the end of the year.
keep someone sweetBRITISH
COMMON If you keep someone sweet, you do something to please them so that they will treat you well in return. Remember to tip the barman to keep him sweet. I like to keep him sweet because he's quite useful to have on our side.