For 2 x 9 miles or even 1 x 18 miles there's absolutely no need to use any energy drinks or gels ever.
Gels should be used for emergencies and racing where there's no opportunity to get any proper food down. Too many cyclists are being fooled by all this marketing crap into thinking they will see some performance benefit from using gels or energy drinks even for short rides. The truth is all they probably do is stop them from losing as much weight.
This information is spot on, too much crap published that you need this and that to perform. I myself have stopped using energy drinks and gels on all my rides and I have found that providing I have eaten well at home and not junk food, I can do hard hilly rides up to 80 miles on just water and electrolytes with no lack of performance. Before, any ride over an hour and I would use energy products, but I have now seen the light, on club rides, events, etc, I still use them as I do not want to become unstuck as I have no fuel in the tank. Weight loss is also improved as mentioned
On rides now I cover for the eventuallity of running out of steam by carrying a couple of gels and also energy drink powder, which I have discovered that those small plastic bottles that are now all the fashion for breakfast containing youghurt etc are ideal, actimil I think, one bottle holds exactly 65grms of energy drink which is the maximum I use in a bottle, so if I run out of steam, I just empty it into a water bottle.
In my experience, their is a fine line between being unfit and running out of energy, and its too easy to blame the wrong one.
No matter how much petrol you put in a fuel tank, it will not help a knackered engine go