I think what you are really asking is how to make inverted sugar. This is when you break the sucrose down into fructose and glucose to make a more highly and easily fermented sugar.
I usually do this for my trippel. To make it I measure out the amount of sugar I am going to put in to my recipe, in this case a pound. Put in a sauce pan with just enough water to make it a little liquidy, and not burn to the bottom of the pot. If you add a lot it will just take longer to heat to temperature
Citric acid is required to invert the sugar, at a little bit of lemon juice or citric acid powder. Not much is needed. A pinch or two. I've actually squeezed a whole orange into it to give it an orange flavor.
MAKE SURE YOU USE A CANDY THERMOMETER, otherwise you will burn it.
Heat the sugar to 300F and immediatly pour into a cookie sheet with wax paper on it. This will make clear hard crack sugar. Let it cool and break into shards when hard.
If you would like to make darker sugar hold the temperature of the pan between 260F and 275F until the desired color is reached. Add a spoon full of tap water to prevent the sugar from going over 275 any time it's needed. For dark colors it could take a few hours. Once the color is reached, heat to 300F and pour into pan.
I add the sugar before the boil so that is fully dissolves.