The three main sources of energy in our bodies are carbohydrates, protein, and fat. With that said, a diet that consist of these three things will give you the necessary energy throughout the day.
If you want energy for something like an athletic event, then you want to eat things like bananas, and on top of that drink stuff like Gatorade during the event. Complex carbs are a great source of energy too.
However, if in general, you want a quick boost, like let's say you wake up feeling tired or in the middle of the day you feel tired, then it is in fact your diet, like chillen and them said. You lack something, and you should start writing down what you're eating, and whether or not it fits into the daily requirements of the three sources of energy.