Oddly enough, the only direct train from Lisbon to Madrid, and vice versa, is a night train. So, since we had no other way to get from the capital of Portugal to the Madrid airport for our flight home, we booked a 4-person sleeping cabin for $110 per person. Expensive, I know. When you compare our crowded, bumpy, noisy, 11 hour night on the train with a stay in an equally expensive luxury hotel, it's a little depressing. But the experience was valuable for my kids, and I'd do it again.
I slept fine (with just a little help from a good pair of earplugs and a double dose of Advil PM), and my son and daughter said they slept alright. But my husband had trouble. He's about 6'1", and the bed was too short for him. The beds are also somewhat narrow. He said he hardly slept at all.
As you can see from my photos, the cabins are narrow with little room for luggage. The bed linens are okay and the blankets aren't needed because the room gets stuffy and warm in the summer. In the corner is a small sink with running water and each passenger is provided a little gift pack which includes earplugs, a bar of soap, a travel toothbrush and toothpaste. Nice touch, I think. We felt very safe because the door had a lock as well as a security chain. I did tell the kids to wake one of us up if they had to go to the bathroom at night, though, just to be cautious.
My husband and daughter, who are early risers, strolled up to the dining car before dawn and had breakfast. They both agreed it was a good meal, with fresh rolls and orange juice. My daughter particularly enjoyed watching the sunrise from the train as the Spanish countryside swished by outside the window.