If you just want a catchy title that sounds cooler, then all you have to do is to fiddle around with the words.
However, I feel that you can still come up with a better question. Right now, it could be answered with a yes/no answer (in addition to not being specific enough), and you probably don't want just that. Your experiment involves quantitative measurements, correct (or so I hope)? How do you intend to measure the amount of vitamin c in orange juice?
An example of a better question is: Is the amount of vitamin c present in a 100 ml cup of Tropicana Fresh Squeeze orange juice inversely proportional (i.e. more sunlight -> less vitamin c) to the amount of time that the cup was exposed to direct noon-time sunlight on a sunny, summer day in San Jose, California?
[A much more specific question that tells the reader a lot about your experiment up front, don't you agree?]