Oh Sugar! Less Soda, More Water.

This advertisement is an example of expert endorsement and the influence of credible sources.  By citing sources such as the American Journal of Public Health and  the Journal of the American College of Nutrition this increases the likelihood of compliance because they are credible.  In research such as that of Bickman (1974) and Hovland and Weiss (1951) it is clear that an opinion or information that is judged to be more credible or from a more credible/authoritative source is more likely to illicit agreement. Thus, in this advertisement the sources are credible and are one of the first things the reader sees and therefore they will increase persuasion because of their credibility. 

From Hovland and Weiss (1951) - A figure showing that Journal articles from scientific institutions receive higher credibility ratings than other sources. 

Also from Hovland and Weiss (1951) - a table showing that sources rated as more credible are agreed with more than those which are rated as less credible. 

 Additionally, the advertisement provides a wealth of information about risks and benefits of both beverages.  Consistent with Petty and Cacioppo (1984) providing more arguments increases persuasion, regardless of how strong each individual argument is because less effort is dedicated to scrutinising each argument when there are more of them.

Employing rhetorical questions has also consistently been demonstrated in research to increase cognitive elaboration - or in other words made people think more about the content of the advertisement when it was made relevant to their own lives. (Petty, Cacioppo & Heesacker,1981)

References:

Bickman, L. (1974). The social power of a uniform1. Journal of Applied Social Psychology, 4(1), 47-61.

Hovland, C. I., & Weiss, W. (1951). The influence of source credibility on communication effectiveness. Public opinion quarterly, 15(4), 635-650.

Petty, R. E., Cacioppo, J. T., & Heesacker, M. (1981). Effects of rhetorical questions on persuasion: A cognitive response analysis. Journal of personality and social psychology, 40(3), 432.

Petty, R. E., & Cacioppo, J. T. (1984). The effects of involvement on responses to argument quantity and quality: Central and peripheral routes to persuasion. Journal of personality and social psychology, 46(1), 69.