I like the concept of promoting independent radical ideas, thinking out of the proverbial box. All engineers and scientist alike should be cheerleaders to concepts such as this one.
However all great ideas need to survive peer review and market forces, if ever is going to be of any merit.
The 39 gr. of carbohydrates from the sucrose/corn-syrup have limited chemical catalysis processes at present time to generate the level of energy as compared to present battery chemistries. Yes, there is an apparent smaller carbon footprint to generate that can of soda. However, if you actually do some more in depth analysis, the author fails to be disclose what energy levels her method has able to achieve at present time, and only acknowledges that it does not generate enough energy to make a single call (typical average 3 minutes).
“Ms Zheng, who is now based in China, admitted that current bio battery's would struggle to generate enough power needed to make a call.”
Read more: http://www.dailymail.co.uk/sciencetech/article-1243096/Fizzy-mobile-Nokia-phone-runs-coke.html#ixzz0xorpTQ00
Also to state the fact that the byproducts are only Water and Oxygen, since there are other ingredients besides the sugar and water in the coke formula, so that assertion is half the picture, this brief piece fails to realize that the footprint of the can, and other logistics of multiple refills.
So what is the prognosis as a future energy source?
Very grim from my perspective, her concept has a very slim change to be a commercial viable product other than a chemistry experiment for high schools!