Toast and avocado
Plain yogurt with chia seeds or flaxseed
1/2 cup of cottage cheese with tablespoon of a nut butter
On the other hand, if you just wake up not hungry, you may simply be waking up with low blood sugar. That's perfectly normal since we typically go around 8 hrs without eating. Try something small with complex carbs to get your blood sugar up. Simple carbs like sugar will lead you to crash later. Once your appetite is piqued (usually within an hr), try having something substantial. The best breakfasts contain protein, fiber and fat. Portion sizes are relatively to your body.