The US researchers found that children who drank more soda were more likely to be aggressive, to have attention problems, to get into fights and to destroy other people’s belongings (Suglia et al., 2013).
As Jeremy explains, the study only finds an association rather than a causal relationship between soda consumption and aggression, but the findings leave open the possibility of a causal relationship. Jeremy also discusses efforts to rule out possible mediating factors, including a variety of parental problems.
If I had to bet, I'd say that the link isn't causal or that soda consumption exerts very little direct effect on aggression. My guess is that constitutional differences interacting with parent-child dynamics are behind higher levels of soda consumption and higher levels of aggression.