They usually use a high tech or a very low tech facility in the Middle East or Eastern Europe somewhere and the prisoners are drugged for days and moved around a bit. Or made to think that they have been. Getting that person, it is best to use a' weak link with knowledge ', completely disoriented. So they have no idea if they underground or above ground and have no idea where in the world they are.
Using sleep deprivation and giving them only low protein food, and no contact with anyone but a few masked interrogaters and maybe a translator; too break that person mentally.
Play upon their weaknesses like showing them a really scary bug if they are afraid of bugs. The CIA actually did that to break a terrorist from the middle East. Who they found out in advance, that he was definitely scared of bugs.
Using big vicious dogs on chains that can get really close. Moving the totally immobilized prisoner closer and closer if they don't give the info up. Turn out the lights. Getting them scared or whatever is necessary. Make sure that they know that they are disposable.
Then off course, lots of water boarding
A combination of complete disoreintation, almost no sleep, low protein and certain drugs, lsd and other psychedelics don't really work, I forget the guy's name who tried researching that for 2 or so decades for the CIA, part of MK-Ultra. Truth serums, are largely a failure. Various drugs that from their chemical names; appear or to be strong barbiturates.( back when any house wife who couldn't get enough sleep or any adult could easily get barbiturates) one common slang term for them was goofballs. This because of people who took more; but not a lot more than a therapeutic dose or



. Anyways the effects of a non fatal or a non knock out dose would cause a person to be in a clumsy and drunken like state. Using strong barbiturates with possibly other drugs, was only slightly effective and only on a small number of people.
Basically to get people into a dissociative state and get them to tell the truth. Hopefully in that state; the prisoners would give up names and other info, by being prompted with little bits of info pertaining to what information that they needed. Being in that state a person might tell them what they needed. However, I out smarted a cop once with a bal of .3825, after probably two hours. So I was probably at .4 give or take at one point. (This was due to a faulty liver that didn't process alcohol properly. I should have been at .00 bal.) I was totally fine and then it hit me)( so in a blackout, I out smarted a cop) no details will be provided.
Anyways a dissociative state, can produces anything from what you want to know to absolute nonsense.
Hypnosis, electro shock 'therapy', water boarding, sleep deprivation ect.. while drugged.
Also threatening their families, and showing them their 1-4 wives being arrested along with their adult children
Also taking other close family members, who could have info you want. Make them think their 4 wives and 137 children's lives hang in balance. Along with the 50 or so other relatives that all live in the same 'house'.
Brutal torture is common in many countries and a payoff to have such facilities and do such things is no issue to the governments of certain countries.
Especially if all they are going to do is scare them and mistreat them. Usually using far less brutal tactics then the government of that country would use on suspected terrorists , themselves.
Most of this type of stuff is not reported and many terrorists have been treated worse. Also, they may never know exactly who did it and where it happened. Then possibly off to Gitmo. (Guantanamo Bay) or secret prisons in Eastern Europe, the Middle East or North Africa.
MK-Ultra was supposedly ran from 1953-1973. Using LSD and other drugs on voluteers( who really didn't know what they were signing up for) Using LSD on Volunteers and unsuspecting civilians. Many were volunteers from the Military and CIA. College campuses were a part of some of this. Brain washing, hypnosis, physical, mental and even sexual abuse was used along with sleep deprivation and being drugged. This was part of the mind controlling experiments.
Many of the documents 'disappeared' and the 1975 Senate select committee( aka The Chuch Committee and the House of Representatives and The President had similar programs looking into abuses by the CIA, FBI, NSA and scariest of all, The IRS.
Their was backlash against these agencies and supporters of it. There is to much to get into, especially with a Smart Phone and a stylus. But some claim that these Black OP's continued into the 80's.
There is also the use of propaganda, certain journalists and media outlets involved. This was the wild west of Espionage. There were various presidents( Ford and Carter) who made assassinations illegal and expanded on this.
A lot of this was overturned and changed under President George W Bush, after 911 and 7surveillance programs ramped up and assassinations made legal and all the controversial stuff was normalized in name of National Security and the frightening powers granted to government agencies under the Patriot Act.
The full extent of all this will never be fully know. If you are in the CIA or NSA and you start running your mouth ; it may be closed permanently with an 'accident' or you might disappear forever and the government, will shrug its shoulders ( figuratively speaking)