Question

They have used up their money的同义句？

Answer 1

回答如下：
本句的同义句是：
They have run out of / exhausted / drained / depleted / spent their money. 他们已经用完了钱。
动词短语use up = run out of= deplete = drain 耗尽，用光，用完。例如：
It is said that the world would run out of fresh water in 2050. 据说到2050年世界上的淡水将会耗尽。
The long war of attrition exhausted the strength of both countries. 这场长期的消耗战耗尽了两国的力量。
Surely it is an economic nonsense to deplete the world of natural resources. 耗尽世界的自然资源无疑是一件经济上的愚蠢行为。
He will drain, rather than enrich, the country. 他将耗尽而不是增加国家的财富。

Answer 2

同义句:
All their money is gone.