All the soda pop contain immense amount of sugar. Even diet or sport drinks have it. The influence of this ingredient spread throughout your body. It causes high activity of hormones, blood pressure, changes of mood and even skin inflammations or other dermatological problems.
Moreover, scientists announced that carbon dioxide washes away calcium in human bones. Also, it makes us thirsty even if we drank 5 minutes ago. So, you can have a dehydration while drinking a soda.