Cramps are caused by severe losses of water through sweating. Drinking water before, during, and after exercise can prevent this severe water loss. Salt tablets can aggravate this condition and require the body to need more water. Drinking milk causes cotton mouth.
Cotton mouth is dry mouth due to lack of saliva.
It seems to be a result of emotional stress and a loss of body fluids, not drinking milk. Remember, adequate hydration before, during, and after is key to keeping the body well tuned for competition. Water during exercise causes an upset stomach and slows you down. There is no evidence that supports this statement. In fact, drinking fluids during exercise is very important.