I open a can of sardines and slice open an avocado. Healthy fats and protein, low carb!

Wrap sweet potatoes in foil and roast them in the oven over night. In the morning, grab a sweet potato out of the oven and eat it for breakfast.

This is probably the easiest and most nutritious meal possible.

Oat meal

Oatmeal and one or two hard boiled eggs. It will satisfy your hunger so you don’t over eat and very healthy.

Steel-cut oatmeal is super-easy, set-and-forget (1 cup water, 1/4 steel-cut oats, pinch of salt, Bring water to boil, stir in oats, salt, lower to bare simmer, uncovered 30 minutes, flavor as desired, eat).

But that can get boring. For something a little more exciting, super-nutritious, and almost zero-prep, do a sort of Norwegian-style open-face cracker (no, you don't need "the tubes", but if you can find them, knock yourself out). For this I take a tin of fish (usually smoked salmon or trout, but sardines, mackerel, or even tuna would work fine), a piece of cracking toast or a Scandy flatbread cracker (Wasa, knekkebrod), and some kind of "schmear" (a thin spread of cream cheese, sour cream, yogurt, or - my favorite - Trader Joe's Everything But the Bagel Yogurt Dip/Spread). I can get all these ingredients both cheaply and well-made at Trader Joe's (TJ Smoked Salmon in a tin, TJ Norwegian seeded flatbread, and the aforementioned dip). For a little additional oomph toss on tomato or cucumber slices.

Diet Coke.

So much prep going on in these comments.

Half a bowl of Shreddies, half of Swiss Muesli, milk. Tea if you have time, juice if not.

Unless there are dinner leftovers, I usually eat a corn farofa filled with two scrambled eggs, half onion, and a carrot. It's 10min cooking if you plan in advance (grate the carrot and chop the onion), really filling, and... well, you got two vegs and a grain and a source of protein, I'd say that it's nutritious.

Protein shake.

Miso soup is my go-to breakfast. You can get dashi powder and miso paste, then just heat water in the kettle and combine. I love that it’s warm and flavorful, but actually a pretty light breakfast (which I prefer).

Cottage cheese with granola. Similar to yogurt but I think cottage cheese is more palatable. The low fat version (often 1% or 2% instead of whole/ full fat) doesn't have as strong a taste to me and is covered pretty easily by granola if you don't like the flavor of cottage cheese. I also recommend store brand for the same reason—the taste is less strong, it seem, than name brand. For example, I think Daisy cottage cheese tastes a lot like their sour cream and just doesn't work as well as whatever store brand is available (and often cheaper) right next to it.

Sometimes I add a little jam or something too, which is also good

I make steel cut oats in a rice cooker with a timer, so I can put the oats and water in the night before. I've pre-mixed the spices, peanut powder, flax powder. I throw nuts and raisins in when I mix it all together in the morning. For spices it's cocoa, tiny bit of cloves, tiny bit of cinnamon, tiny bit of ginger, pinch of salt.

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.

Microwave oatmeal but with so much water that it's drinkable. Have a pint of that and your body will thank you tremendously.

I always have a bowl of full-fat Greek yogurt with a spoonful of almond butter, a sprinkle of cinnamon, some collagen powder, and a little bit of maple syrup. Easy to scarf down in a hurry and keeps me satisfied for a few hours.

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.