I am seeking after a single word for describing "make something or someone confess". Apart from a single word, welcomed are also idioms.
The phrase structure break someone down has a relevant sense:
to force someone to give up and tell secrets or agree to do something. After threats of torture, they broke the spy down. They broke down the agent by threatening violence. ‒ thefreedictionary.com
Ngrams for force a confession,wring him out,break him down shows that since about 1860 break him down has appeared in print more often than force a confession; and those phrases have appeared far more frequently than wring him out. The phrases are not strictly comparable, and comprehend only one of many possible pronouns, but the ngrams result agrees with what I think relative use of each has been.
I'm sure there are many such words/idioms. An effective one I can think of is "come clean".
come clean (with someone) (about something)
Fig. to be honest with somebody about something.
I want you to come clean with me about your financial status.
come clean to tell the truth, often about something bad that you have been trying to keep a secret
I felt it was time to come clean and tell her what the doctor had told me.
(often + about ) It's time for the Chancellor to come clean about the proposed tax rises.
The phrasal verb wring out can be used
To obtain or extract by applying force or pressure: wrung the truth out of the recalcitrant witness. [American Heritage Dictionary]
This usage is not limited to confessions but may be applied to other information held in confidence or even to other things, such as money.
There is also an idiomatic phrase in US English give someone the third degree
Long and harsh questioning, especially by police, to obtain information or a confession. [Oxford Dictionary Online]
I'd say that such a confession was [coerced] from https://www.google.com/search?q=coerce&oq=coerce&aqs=chrome..69i57j0l5.1367j0j7&sourceid=chrome&es_sm=93&ie=UTF-8
persuade (an unwilling person) to do something by using force or threats.