Do you test your BS with a meter? It could be useful so you know what your BS level is when you feel tired. If your BS is near normal then the problem is not so much that you need to eat something for an energy boost but the problem lies elsewhere? Don't forget you can eat proteins and fats to increase your calorie intake without taking a big BS hit. They may not give you 'instant' calories but at least you are having something to eat without the carb hit on your BS.