Mark1964's spot on. Turbo cider is easy and great. I've always got one on the go. I usually drink it the way it comes (dry). But my wife likes it sweet. You can add sweeteners like Splenda to sweeten at bottling, I.e. Rack to bottling bucket and add sweeteners until it tastes right, then add your priming sugar. Or a Youngs wine sweetener.
Or, what I tend to do is pasteurise to kill the yeast -Which is a bit more tricky. Sweeten with sugar until you've got the correct sweetness, then add your priming sugar and bottle. Wait a week until it's carbed (use at least one PET bottle to check progress - bottle goes hard), then submerge the bottles in 80c water for 5 minutes to kill the yeast and thus halt carbonation (don't fill your bottles too much or they'll pop). Plenty of YouTube vids on the subject of back sweetening and pasteurising