I am going to offer some suggestions that could be useful. You need a high carbohydrate snack before a class, light enough to not bother your stomach, but enough to replenish muscle glucose. Try a banana and yogurt, cereal and milk, juice and pretzels, bagel with jelly and juice. Be sure to get a breakfast and lunch that includes protein. You may actually be sacrificing muscle mass with all this exercise and not enough protein.
Studies show that protein is also broken down for energy in high exercise individuals.
Carbohydrates are the main fuel for your body, so do not skimp. Your alertness suffers. In your case, sports drinks are helpful to replace sodium, potassium and glucose as well as fluid loss. I hope this is helpful. This information is not intended to be a substitute for professional medical advice.