I recommend going to your local library and searching for the memoir called "One Bullet Away: The Making of a Marine Officer." Beginning on page 149 the author, Nathaniel Fick, spends a couple dozen paragraphs recounting his weeks at SERE.
I can't fit it the whole section in my answer, but here are a few excerpts you'll find interesting:
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"The first few days in Warner Springs were dedicated to hands-on application of skills we had learned in the classroom -- navigation, camoulage, signaling, and foraging. Nothing new for a Marine grunt. We slept in piles beneath tiny squares of parachute silk, struggling to keep warm. In six days, I ate one carrot, a few handfuls of wild barley, and a little bit of rabbit. Much of SERE's fearsome reputation was based on this starvation, and it slowly degraded our decision making, putting us in a more vulnerable state of mind.
Toward the middle of the week, our final exam began: the simulated plane crash behind enemy lines, evading the packs of men and dogs pursuing us, and, when captured, resisting interrogation in an isolated prisoner of war camp. No one evades the whole time; everyone goes to the camp. But the one thing the staff can't control is the clock -- the course ends when it ends. The trick is to avoid capture for as long as possible, spending time on your own terms in the woods rather than at the mercy of your captors in the camp."
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Fick goes on to write that, especially without much food or sleep, the simulation seems very real and that, at times, he forgot that it was just a training exercise.
As far as the torture goes, it's all closely regulated to stay within safe limits, but it's still terrifying for the participants. From his written description, it mainly consists of being punched and slapped and being subjected to solitary confinement in dark, claustrophobic boxes.
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"When SERE ended, the staff carefully debriefed each student on his performance. A Navy petty officer sat with me in an empty Coronado classroom.
'So, sir,' he said with a smile, 'how long do you think you were locked in the box?'
'An hour, maybe two,' I replied.
'Eight minutes.' [replied the petty officer]"
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The main aim of SERE is to train you to maintain careful consciousness of your actions even when extremely uncomfortable and disoriented. They don't want you to spill all the beans to the enemy just because you couldn't handle the stress.