Two things -
I agree with Roger on page ten, re low glycemic index carbs before exercise such as an hour walk. That's the kind of advice I used to read in Runners World magazine. You might look at their website.
Protein is good in the morning for the brain, but not so much related to energy for exercise.
I looked up San Pellegrino water just to see what's in it -
http://www.aquamaestro.com/innerview.asp?catid=18
Mineral waters vary a great deal in content, a matter I learned with some amazing menu at a restaurant about five years ago. Some are bubbly (con gas) and some "still".
I'd look into carrying one of those drinks with electrolytes and not too much, if any, sugar, or drinking mineral water and carrying a banana...