My quick alternative is a bowl of yogurt. I personally love plain Greek yogurt, so a scoop or two of that with some berries, granola, and honey and I've got myself a delicious breakfast. You might also be surprised how filling a grape fruit is.
Something high in protein will fill you up for longer and give you energy throughout the day. Protein also aids in muscle growth provided you get sufficient exercise, so something protein-rich like eggs would be great. For extra nutrients you could add some avocado and seeded toast. Even an apple or a banana (or both) would be a great alternative. Nuts and seeds are also great if you would prefer that. Sugar or fat-rich foods will give you an energy spike and then you'll experience a crash, and sugar causes the stomach to expand, increasing your appetite. Stick to the healthy options 🙂
For my first meal of the day is oats + fruits. You can change fruits to chocolate one day and mix oats with many different types of mixtures.