To give sb. a taste/dose of their own medicine
Definition: to do the same bad thing to someone that they have often done to you， in order to show how unpleasant it is.
【世博精解】
“给某人一剂他自己的药尝尝”，这句惯用语同我们的“以其人之道还治其人之身”异曲同工，意思是用某人对别人的手段对付他，也让他尝尝其中不好的滋味。比如如果Jack对别人很粗鲁，那么别人也同样粗鲁地对他，那就是give him a taste of his own medicine. 例句如Did you see those two people cutting in front of us in line just now? Let's cut in front of them and give them a taste of their own medicine! 虽然我们不鼓励这种以其人之道还治其人之身的做法，但是学会了偶尔用用还是蛮过瘾的，看这一例： I saw you pushing my brother yesterday... maybe I should give you a taste of your own medicine! （或许我也应该让你尝尝挨揍的滋味！） 有时候，a taste of one’s own medicine也可以单独用：He's always interrupting people when they are talking; what he deserves is a taste of his own medicine!
Example dialog:
A: Look who’s coming！
看谁来了！
B: At last she’s coming! She’s always turning up late for me so I thought I’d give her a taste of her own medicine and see how she likes it.
她可算来了！我邀请她时，她总迟到. 我老想着哪天我也得让她尝尝她的客人迟到的味道，看看她喜不喜欢。