Easy one first.
No, I haven't put the baldder in the freezer. I've read about this, but never had to do it. Cleaning properly seems to work, rather than just killing the bugs and leaving their corpses to be consumed next time I ride.
The SIS GO Electrolyte Energy - Fuel, is not just an energy drink. It is only distinguished in content from the SIS product dedicated to electolyte replacement by about 2% more maltodextrose, ie 92% instead of 90%. So I thought I was safe to go for the electrolyte energy option. As I said, it works for me, and I did try the pure electrolyte option, as well as the dioralyte route.
As for the food aspect. I eat well as a normal way of life. On the morning of a ride, I eat a humongous bowl of cereals, nuts, seeds, fibre, oats etc. This is all stuff at the correct end of the glycaemic index, ie slow burning. I eat the funsize Mars and the energy bars because they are light to carry, easy to eat, and they provide what I need, when I need it. I once had a "proper meal" at lunchtime and I was bloody near crippled trying to ride afterwards as my body diverted resources to digesting it. Ever since, I eat well the night before and the morning, and then eat lightly. As I said, it works for me. I fully accept that we are all different and I would suggest that what works for one may not work for another. The key is to try a few alternatives until you find one that works for you.