If you’re just desk jockeying for 10 hours, I’d say skip the breakfast entirely. A nice iced coffee (black or splash of oatmilk) goes a long way towards curbing hunger.
If you absolutely MUST eat in the morning, a smoothie is nice and cold, quick to make, and can be as high/low in calories as you desire. I make mine with a banana, frozen strawberries, protein powder, peanut butter powder, and soy milk (~300kcal, 30g protein) but I only have one on days I go to the gym (4 days a week)
I thought it meant ‘once every other carb’…?