sweeten
verb [ T ] uk/ˈswiː.tən/ us/ˈswiː.tən/
(TASTE)
使变甜
to make something taste sweet
The apple mixture can be sweetened with honey. 什锦苹果里可以加点蜂蜜变甜一些。
Compare: unsweetened
(MORE PLEASANT)
使更具有吸引力，使更诱人
to make something more attractive
The phone company threw in two month's worth of free calls to sweeten the deal. 电话公司用两个月免话费的优惠让这个服务方案显得更诱人。
使…更高兴，哄…开心，使…更友善
to make a person or a mood happier or friendlier
I think you should try to sweeten him up before you ask him for the loan. 我觉得你开口向他借钱之前应该先哄他开心。