Bread, butter, cheese and cold cuts.

Breakfast burritos: Scramble up some eggs and whatever you've got, toss it on a tortilla, throw some cheese and salsa on and you've got a hearty, easily transported meal that's relatively easy to make.

Oatmeal: Make your oats, toss in nuts, berries, whatever: Yum!

Sausages: I just stick them on a baking sheet, bake for 10 minutes at 400F, flip, 10 more minutes, and they're good to go. Save even more time by precooking them, storing them in the fridge, and microwaving them on the fly. Add some toast and guac, maybe a piece of fruit, and you've got some decent nutrition.

Breakfast shakes: Lots of nutrients and little to no prep time. Not super filling but enough to get you through at least the first few hours of the day.

Egg on toast. Takes just a minute or two to fry/scramble an egg and frankly you don't have to watch it like a hawk the whole time so you can make your coffee or whatever while it's frying. Throw a slice or two of cheese on top while the egg is still hot

Cum

Chia seed pudding is super simple to do. Put 3-4 tablespoons of chia and one cup of liquid (e.g. milk) in a jar, throw it in the fridge and let it sit overnight. Add some fruit to it in the morning if you want flavor. It is basically flavorless if you don't.

Avocados toast is pretty easy. Toast some bread. Mash on some avocado. Sprinkle with garlic salt or everything seasoning. Delicious and healthy!

I dunno about nutritious, but I sometimes like baking oat cookies and having them for breakfast, super easy to eat and honestly probably as bad for me as regular cereal. Do want to try and make them "healthy" though