Sports energy gel washed down with bottled water.
Probably seems a bit odd to some but I've spent years doing triathlons where you need quick energy, something that won't upset your stomach or have you wanting to go to the toilet half way through. I've developed a routine which means no solid food less than 4 hours before the event, a gel about 20 mins before, and for longer punts (3 hrs or more) I bring another gel which I take at a convenient break usually about 2 hrs in.