An energy gel is 20-25 g of fast carbohydrate in a sachet, built for taking fuel on the move in an endurance event. Most mix glucose with fructose, which raises how much the gut can absorb per hour beyond what glucose alone allows, and most carry sodium. They need water alongside them: taken dry, the concentration pulls fluid into the gut and causes the cramping gels are blamed for. Outside long training and racing they have no purpose.