You need sugar (carbs) to exert energy so you can actually train well. Eating a nutritious snack about 45 minutes before hitting the gym is a great idea. That quick meal should include carbs and protein which means berries, yogurt, banana, almond butter, etc. If you’re hungry and choose to eat actual food as opposed to having a protein shake or a smoothie, pick something with good fats and a lot of nutrients. A small snack of 200 calories will do. Anything more than that can cause stomach cramps, pain, or nausea. Your body will be preoccupied with digesting the food instead of getting nutrients to the muscles.