Yes, you should drink liquids during a half marathon. You should consume adequate water and sports drinks to meet your sodium needs and avoid dehydration. Some runners can lose upwards of 2-3% of body mass while running, which can compromise exercise performance and cognitive functioning [1].  Not taking in enough water and electrolytes during a half marathon can also lead to dehydration or hyponatremia, which can make exercise more difficult, increase fatigue, increase heart rate, cause difficulties regulating body temperature and more [2, 3]. To prevent this, consume sports beverages or sports products that contain sodium [2]. This will continuously replenish your body with sodium and liquids, so you do not run out of essential nutrients during the half marathon.