It's best not to use sugar for a starter. The yeast need the nutrients in the malt. Plus yeast use different methods for processing different sugars. Using malt in your starter conditions them to be ready to ferment your wort. Your lag time will slow if you use sugar instead of malt.
If you have to, go ahead and use the sugar, but make sure the yeast have fully ferment the starter before you use it. Also it would be best to chill the starter overnight before you use it and pour of the 'beer' that the yeast have made. This will not only get rid of the cidery beer, it will stop the yeast's metabolism and help them adapt to the wort quicker. Just let the starter temp rise to about room/wort temp before pitching.