Don't underestimate the addictive potential of the caffeine and sugar combination. As I've often said, cola drinks are drugs, not just sweet-tasting thirst quenchers. Caffeine is well-known for its effect as a natural stimulant. It also acts as a diuretic and can be a urinary tract irritant. Stay away from caffeine if you have migraine headaches, a tremor, anxiety, insomnia, cardiac arrhythmia, coronary heart disease, any urinary disorder, prostate trouble, fibrocystic breast disease, or premenstrual syndrome.
Sugar also has strong drug-like effects in some people.
Sugar can give you a rush of energy, followed by a metabolic crash soon after. This cycle is extremely disruptive to the body's energy cycle and can trigger disturbing mood swings. Coke has been used as a remedy in certain situations. I saw one study in which it was used successfully to remove a mass of food stuck in the esophagus. It's also sometimes used as a contraceptive in the form of a postcoital douche.