You have no energy because anything more intense that walking burns carbs and if you're not well carbed (liver and muscle) before you go to bed, you're going to struggle the next morning if liver glycogen is low. On the other hand, if you eat anything that raises your insulin before cardio, you burn more carbs.
There are some very low GI carbs that don't raise insulin but provide some energy and can be used as a breakfast before cardio.
I tell my clients to do their cardio am after the weights. Then they can eat some carbs prior to exercise and still burn fat after lifting when they do cardio. The lifting shuts off the insulin response and puts you in a fat burning mode even after a light carb breakfast.
or, just powerwalk for an hour on an empty stomach then you only burn fat and can maintain the workload without eating carbs.
W6