That whole story about benzene from soft drinks is sheer nonsense.
Many soft drinks and also other processed drinks and foods contain benzoic acid (or salts derived from this). Benzoic acid is C6H5COOH. This compound is fairly innocuous. In order to make benzene out of this, the -COOH group should be replaced by a single H-atom. This, however, is remarkably difficult and requires quite extreme conditions, which certainly are not present in the human body.
Drinking a lot of coca cola is not healthy at all, but there are other ingredients then which are more harmful (most notably the loads of sugar in the product and its fattening effect on the human body).