Give this a good stir, cover it, and set it into the sunniest part of your house/ balcony/ garden. You will have to give this a good stir every few hours on the first day. If possible try to keep shifting the vessel to sunniest part, as the shadow of the sun keeps shifting.
If its not possible for you to stir the mix, throughout the first day, make it in the evening and stir it for 20 minutes or so, as soon as you make the mixture. No heat is required. The point is to dissolve as much of the sugar as possible.
Set it in sun,the next morning.