It is best not to drink alcoholic and caffeinated beverages when dehydrated, according to Cleveland Clinic. Caffeinated drinks include sodas, coffees and teas, which tend to increase dehydration by removing water from the body.
Fruit juices and fruit drinks can also promote dehydration, Cleveland Clinic states. These drinks often contain too many carbohydrates and too little sodium to promote healthy levels of hydration during exercise. Signs of dehydration include muscle cramping, fatigue and flushed skin. To avoid dehydration while exercising outdoors, drink 6 to 12 ounces of water or specialized sports drinks at regular intervals of 10 to 15 minutes.