Sleep habits? We only know about Bertolt ^^
Eren has rather sporadic sleeping patterns. He had mild insomnia, and sometimes finds it difficult to fall asleep/stay asleep at night, which leads to him taking naps at old times during the day (and often in really odd places where you wouldn’t expect to find a sleeping boy.) He tends to sleep curled up on his side in a tight ball, which is usually how he fits into such odd places as in desk chairs, window alcoves, or under/on tables. Also suffers from pretty intense nightmares that also complicate sleeping.
Mikasa tends to fall asleep easily and wakes up just as easily. Her body knows how long it needs to sleep, and will let her know if she’s not sleeping enough. Like Eren, she has pretty frequent nightmares, but she is usually able to get back to sleep if they’re bad enough to wake her up. She’s taken to keeping an extra pillow and/or stuffed animal close so that she can hold onto it to help anchor her to the world when she tries to fall asleep post-nightmare. It works. She’s also just comfortable sleeping with something (or someone) held close.
Armin is a very deep sleeper, but if he does get woken up in the middle of the night, he finds it incredibly difficult to fall back asleep and will be grumpy the next day. He needs a minimum of five hours of sleep to function, and only goes less than that during a hectic finals week, (but he’s not really living, more like coasting through life if he hasn’t gotten at least five hours.) But he’ll be pretty grouchy unless he gets at least seven. He’s a very active sleeper, and is known for stealing pillows (if sharing a bed with someone, or sleeping in close enough proximity to do so.)