I had to get up at 3am to catch a flight not long ago. Knowing I wasn't going to eat much on the plane, and wanting to get as much sleep as I could beforehand, I had some hard boiled eggs, microwave bacon and a cup of plain full-fat yogurt with a splash of DaVinci syrup in it. Took about 3.5 minutes to fix (while the bacon was zapping I stirred up the yogurt and cut up the eggs.)

That helped me last until afternoon, when I had a couple of Atkins bars stashed in my carry-on.

I tried the shakes and just couldn't force myself to like them.