yogurt or eggs or nuts
If you can't tolerate dairy you can't probably tolerate yogurt though, because the fermentation process makes yogurt very low in casein
I can't have breakfast when I wake up because it makes me sick, probably the combination of feeling tired from recovering from sleep and sending all the blood flow the stomach. Animals and tribal populations don't eat first thing in the morning, we don't need to. The proof is that when a person have his blood tested in the morning after a night fast, his blood sugar is normal (unless he has diabetes or other pathologies) meaning we don't need breakfast to raise a low blood sugar.
So I wait two or three hours to have breakfast, which becomes like middle morning snack at school.
I can't have many carbs in the morning, they make me sleep and excerbate my brain fog and muscle soreness.
I tolerate more carbs and sugar in the evening or even late afternoon, but morning I have to stick with proteins or fats, at most a small slice of bread.
Fruit is a no no for me in the morning.