Take another vessel and put sugar and water in it. Let the mixture boil to make a syrup. If you want you can put two drop green Colour. Make a one string syrup, which is not very thick and do no settles down instantly. Put all the parwal into this syrup and boil until their colour changes. You will experience a beautiful change in the colour. Flip the side of the parwal while boiling it. Turn off the flame, cover the vessel and leave it for 1 hour in the syrup. Let them get sweet.