One of these hotels is the Capsule Inn Akihabara in Tokyo. The capsules in this "tube hotel" measure only 2 square meters (1m x 2m and 1m tall), they have 169 of these rooms. Most of the capsules are for men, there are only 24 for women.
Each capsule unit has a TV, radio, alarm clock and adjustable lighting and all of these devices can be controlled in a sleeping position, as if you were in the cockpit of an aircraft or a spacecraft.
There are multiple floors with capsules and I suppose that most of the capsules are stacked in big rooms. Fortunately there are blinds so you have at least some privacy. You can also do some more work on your notebook in the rooms, WiFi access is also provided.
On each flour with capsules there are washrooms, on the second flour there's a public bathing room for men only and on the top flour there's a lounge for women only.
The Capsule Inn Akihabara charges 4,000 Yen (almost $33) per night, you can check in from 5:00 PM and you have to check out before 10:00 AM.