I mean, yes, it's totally possible to eat 1000 calories for breakfast. I still don't think it's typical. Why would you even want that OJ after eating 3 whole cups of cereal? Also, how do you not just end up hyperobese eating like this, assuming you're not just cutting the calories from a later meal. A 300-Calorie/day excess will put on nearly 40 pounds every year, and I'd expect anyone eating 1000 Calories for breakfast every day to either be very active or else be eating at least 300 Calories too many per day.
Also, a cup of Cheerios is 100 Calories. So 3 cups is still only 300 calories. Add milk and you're at maybe 500 Calories. Even Honey Smacks is only 133 Calories per cup. If you eat 600 Calories of Honey Smacks and milk, I hope you'd consider that enough sugar for breakfast. Or else I hope you're training for a marathon.
Today I still eat cereal but usually a cup at most, and either without milk or with almond milk. I started on a diet (the south beach diet) about 5 years ago and I lost over 100 pounds. I don't consider myself to be following any specific diet nowadays, I'm just more healthy and smart about what I eat, and I eat much smaller portions. I also exercise 3 times weekly, and need to find time to increase that even more.
I will say when I first started my diet I dropped cereal and just ate scrambled eggs almost every morning. My morning energy levels skyrocketed.