While you can just use table sugar and salt, getting some of the right stuff should lead to a more effective energy drink and won't cost much more. Also, using maltodextrin instead of plain old sugar means you won't have a sickly sweet drink.
Myprotein.co.uk is where I get all my stuff from. I make mine with 2 parts malodextrin to 1 part fructose. I sometimes add electrolyte powder (better than salt which is only sodium) and for races will often add some caffeine powder. Mixed with some fruit squash (usually grapefruit juice for me) it tastes ok and is very, very, very similar to the brand-name drinks, but for a fraction of the price.
However, I only use energy drinks for racing and long/fast rides. For regular rides up to a few hours there's no real need for an energy drink (though a sprinkle of electrolyte powder is often a good idea).