It looks like most of the current suggestions aren’t very high in protein, which is really important for kick-starting your metabolism and helping to keep you full. Cottage cheese with some berries (which are higher in fiber, vitamins and antioxidants than most other fruits) would be a good bet. You could also have oatmeal, as suggested, but I would look for a high-fiber variety and have a hard-boiled egg with it (of course, you would have to prepare that in advance.)
Also, if you’re traveling in the US, you will almost certainly be near a Starbuck’s (it seems hard to avoid them these days). They have a spinach-feta-egg white wrap that has a good mix of protein, fiber and fat that should keep you full until lunch, and it is only 280 calories:(note that it is fairly high in sodium, though).
Also consider bringing along individual oatmeal packages. It is usually easy to find hot water at a coffee shop or to heat water in in-room coffee machines or tea kettles to mix with the oatmeal.
also try Overnight Oats. If this is a road trip or you have access to these items, combine the following in a resealable container (I usually carry one or two while traveling and use it for various purposes during a trip, they come in handy):
- rolled oats
- nut/seed butter (peanut, almond, sunflower any other) for a more filling and protein rich meal [optional]
- chia seeds ( a tsp/serving is a good measure) [easy to carry]
- dry fruits & nuts/seeds (depending on allergy)
- sugar (if available, if necessary)
- water/milk use non-dairy milk from shelf stable package
Fruits are always the best option for the breakfast if you cant cook.
and leave in the fridge overnight. In the morning, add pieces of fresh fruit like banana, apple, strawberry etc. and enjoy!