Routine:

Normally, Shepard checks all of her messages, assembles a tiny ship, forgets to feed her fish/overfeeds her fish, and fills out about 1/4th of the paperwork Miranda has waiting for her before sleeping.

On Sacrosanct, she double checks with whoever's on rotation or going on guard rotation. Scans the network like a CB with a direct line into enemy camp, checks that her pistol has a full clip, double checks the welds on that damn vent, and possibly adjusts her shield modulation before sleeping.

Clothes:

Armor. Oh, you mean for sleeping? Armor, possibly underarmor. There were a a few brief stints where she enjoyed sleeping in some pyjamas but that proved to be a bad call, all around.

Sleeping Position:

Is Paranoid a sleeping position? Shepard can sleep in any position so long as she has her weapon on her. There's really very few situations where it isn't on her, but on those occasions, she sleeps facing the entryway.

Quirks:

Shepard sleeps in arm's reach of a gun at all times. The only two times she forewent this tradition were during her stint on Torfan (Hey, if they wanted to come out of that bunker and try to off her, she'd give them a little hope. Then she'd break their necks. Damn Batarians.) and during bootcamp (Because she was freaking out the other cadets)..

Fave Position:

You know, Garrus has told her the word for that probably fifteen times and damn if she can ever remember it. Turian words all sound suspiciously like metal flanged German.

Any seekrits?:

Yes.

Fetishes:

Who doesn't like listening to Garrus talk, honestly? It's one of the things she misses most about regular missions, she doesn't get the thrill of hearing him announce kill-shots over the radio while she's running an adrenaline high.
ALSO HE LOOKS LIKE A DINOSAUR!?

Quirks:

She's dating an alien vigilante who used to be a cop. I don't know if quirky is the word for that, but it's definitely something.

Fave/Least Fave Food:

Shepard's favorite food, bar nothing, is Tiramisu. Shut your face. It's desert and it's soaked in alcohol, what the hell else could you want from life?

Her least favorite food is Alliance MREs. Particularly the Italian package. If she believed in god, she'd have questioned his existance upon eating whatever that thing contained. She may not be able to boil water, but damn, that is not garlic bread.

Fave/Least Fave Drinks?:

Shepard's favorite drink is Batarian Ale. It is the only redeemable item to come off that planet. Her least favorite drink, the powdered wine substitute included in the afforementioned MRE.

Can they cook?:

AHAHAHAHA. No.

Do they have all the table manners?:

She has been known to employ all the table manners at fancy parties, but no. Shepard does not have them all. Good thing the aliens on her crew don't know better and the humans are too poilte/afraid to mention it.

Quirks?:

Shepard has a fascination/love of crazy straws. She never gets to use them, being that she's a badass. Human bartenders never give them to her, but every time an alien bartender accidentally sends one over in a drink, she gleefully uses it. When prompted, it's either because she doesn't want to draw attention, or its part of her cover.