Conversation so far:
what is release referring to with Ai Weiwei?
On 22 June 2011, the Chinese authorities released Ai Weiwei from jail after almost three months' detention on charges of tax evasion.
what evidence did the Chinese authorities have on Ai Weiwei in regards to tax evasion charges?
Professor Wang Yujin of China University of Political Science and Law stated that the release of Ai Weiwei on bail shows that the Chinese government could not find any evidence.
how was Ai Weiwei treated in prison?
On 24 June 2011, Ai Weiwei told a Radio Free Asia reporter that his detention by the Chinese regime was hellish, and is forbidden to say too much to reporters.

Question: what did they do to him?
Self-contained rewrite: what did they do to Ai Weiwei in prison?