What is a nutritious, filling, and easy to eat breakfast for really early in the morning?

Granola with yogurt.

I get a fairly low-sugar granola, or make my own (see 'food wishes - granola' on YT) and portion it into tupperware containers, 1/2 cup each. Then I put on 1/2 cup greek yogurt (the real kind, not the sugar-loaded kind) and freeze like 10 of them at a time. In the morning, i take one, add 1/2 cup oat milk, maybe some extra dry or frozen fruit, and by the time i get to work, its defrosted but still cold, mushy but still crunchy. Should be relatively low in bad sugars and pretty tasty.