What should I really eat for breakfast? (and snacks too)

You should eat whatever you like for breakfast that will keep you satisfied until your next meal. If you want something smaller and a snack before lunch then that is fine. If you want to eat a little larger breakfast and then not snack until lunchtime that is fine too. And you don't even have to eat breakfast if you don't want to. It really is just personal preference. I usually eat greek yogurt, fruit, boiled eggs and coffee for breakfast. If you are looking for breakfast ideas then that is my suggestion, but it isn't necessarily something one "should" eat. That is just what I like to eat because I like it and it is easy to eat at my desk.

There is no rule that you have to eat a certain kind of food for breakfast, or that you have to eat breakfast at all. The "most important meal of the day" is utter marketing hype. Lots of us prefer not to eat anything for breakfast, either because of being on an intermittent fasting program, or preferring not to eat before a morning workout, or whatever. All you have to do is meet and not exceed your calorie target for the day; everything else is optional.

I love steel cut oats cooked in almondmilk and blue berries with hemp seeds and maple syrup. Other days I like egg white omelettes or yoghurt. Breakfast is whatever you want to eat

I don't care much for breakfast, but often get a little snacky an hour or two before lunch, so my dietitian recommended a cup of Greek yogurt with high fiber cereal mixed in (I prefer the Trader Joe's High Fiber Cereal, which is only 80 calories a serving and surprisingly sweet given the fiber content). It's simple and filling.

Dunno if what I do is of use to you but here goes...

My calorie goal at my current weight is 1750 cals. I go big on breakfast (500-600 cals) and small on lunch, focusing on protein at breakfast, but I like to end with something sweet, so I have some fruit. Its summer so right now I'm having exotics (eg: lychee, melons), but a wiser choice year round is apples because of the fiber content.

So--2 eggs, 2 bacon, hami melon (a summer-only fruit), green tea, comes out to about 500 calories depending on how much melon (that's for about 300g, which is generous portion). Microwave the bacon, use the paper towels from the bacon to grease the pan for the eggs. For variety you can spiff up eggs without adding calories by using truffle salt.

Notice the lack of toast. 2 pieces of bread can be 220-300 calories, then add another 50-100 calories of butter and 60 calories of jam and you're up to 300+ calories just for the toast. Not Worth It.

I also like Japanese food so sometimes I'll have grilled salmon or mackerel on (a limited quantity of) high quality rice with a couple of tablespoons of Japanese pickled vegetables from an Asian market. This usually comes out around 600 calories because I'm overly generous putting sesame seeds on it. This can also be made ahead and eaten cold, which might work for you since it sounds like you bring your breakfast to work and eat it there. If you want to be a bit more structured about it go to "cooking with dog" (the dog, Francis, narrates in a French accent) on youtube and look up Chazuke.

For arcane reasons, the bio-accessible carbs in rice decrease if it sits awhile after being cooked, but how much is hard to quantify so you have to use the standard freshly cooked values in your logging. Just know you can gain a slight advantage by using rice cooked the night before. (you can look this up using google scholar; I found it while trying to find out which varieties of rice have the lowest glycemic index)

If you really need to cut the calories but want to feel fed, home-made miso soup (not the instant packet kind) works well for me and comes out at under 200 calories. Suggest making the dashi/miso broth ahead, bringing tofu, wakame seaweed (which is dried), and any other veggies you want in it in a separate container, assemble and microwave at work. If you are going to do this it is worthwhile to find a local source for tofu because most national brands go sour before they get to you. *Fresh* tofu is a wonderful thing.

Bacon... The answer is definitely bacon.

Breakfast was the first thing I dumped when my wife and I started dieting 4 ish months ago. Best decision I've made so far. That took 200-300 calories of useless refined carbs in the form of cold cereals and deployed them into lunches and dinners where they could actually do some good in the form of nutritionally sound foods. Plus, after a week or so my body had completely adjusted and I wasn't hungry at all in the mornings ... and haven't been ever since. That was an eye opener. I literally have no interest in food in the morning at all, whereas for most of my life I would wake up thinking about breakfast.