Any hydration packet (chose the brand (liquid iv, lmnt, mtn ops, WA, or tablets)) will work. They are necessary with any exertion where you excessively sweat. For many hours. But water is also key. When I’m training for Ultras I aim for a specific amount of electrolytes and glucose per hour or two. When I’m coming into an aid station I’m filling up three 500 ml flasks with water. One of those will have a packet of electrolytes to be mixed in one of the flasks. When cramping starts water and electrolytes are very key. But overconsumption to quick can also cause negative problems.