Drink coke alone does not make you gain weight. A lot of stuff play a role in gaining weight, eating too much Without Exercising or not exercising enough.
I would stay away from product that contain simple sugar, like the one in the soda, candy bar.
I would also reccomend drinking juice instead of soda, dringk orange juice it have vita C, or drink, cranberry or rasperry juice it have a lot antioxidant, which is really good for you.
taichi