One soda a day is not going to be horribly detrimental to your health. However, you may notice the beginnings of some weight gain. It has been shown that high-fructose corn syrup may make it harder to know when you are full, so you may eat more than you normally would. Additionally, there are a lot of empty calories, meaning calories without nutrition.

Drinking one can of soda a day may not sound like a lot, but it is damaging.  Soda consumption has been linked to child obesity, and tooth decay, and can inhibit proper food digestion.  If you drink the one can, it will suppress your appetite possibly keeping you from eating nutritionally dense foods.