get blood out of/from a stone idiom
像是从石头里榨血（指要从某人身上获得某物或探听某事极其困难）
to make someone give or tell you something, when it is extremely difficult because of the character or mood of the person or organization you are dealing with
Persuading Chris to buy a round of drinks is like getting blood from a stone. 说服克里斯出钱给每个人买杯喝的几乎不大可能。