What are some high calorie quick breakfast snacks?

So for most of my life, I have skipped breakfast and rushed out of the house with one of those 100-calorie k-bars/nutrigrain/ breakfast bars.

So I have to take a few really high-dosage antibiotics in the morning. So my body needs something that has more calories and probably gives me more energy since the meds wear my body out a lot. I usually rush to work every morning so I dont have time to make breakfast.

So what are some morning snacks that I can get at a grocery store that are high in calories/gives me more energy?