Making rock candy is surprisingly easy and takes very few ingredients. Here's what you'll need to get started:
- 1 cup of water
- 3 cups of granulated sugar
- Food coloring (optional)
- Flavoring (optional)
- Popsicle sticks or wooden skewers
- Narrow drinking glasses
Start by bringing the water to a boil in a medium sized saucepan. Reduce the heat and start adding sugar to the water, adding about 1/2 cup at a time. After each 1/2 cup, stir until the sugar is dissolved in the water before adding more.  Continue adding the sugar until no more can be dissolved in the water. You may find that it takes longer and longer each time for the sugar to dissolve. It is important to keep going, though and not to give up too soon. Set the water aside for about 15 minutes to cool.
While the water is cooling, prepare your popsicle sticks or skewers by dipping the ends of them in water and rolling them in granulated sugar. This provides a surface for the sugar to grow on. Allow the skewers to dry.
Line up several narrow drinking glasses on the counter. Add any colors or flavors that you want to each glass. You don't need a lot of food coloring or flavoring...just a few drops will do. Pour the cooled sugar water into each glass, filling it up close to the top, but not all the way.
Next, take a clothespin and clip it onto each skewer toward the top of the skewer. Rest the clothespin across the top of the glass so that the sugar-coated part of the skewer hangs down into the sugar mixture. It should be positioned in the center of the glass and should not be touching the bottom of the glass. You may need to adjust it in the clothespin until you get it in the right position. 
Set the glasses aside for a week or two to give the sugar crystals time to grow. Once you have enough crystals on your skewer, remove the skewers from the glass. You may need to soak the base of the glass in hot water to soften the crystals so you can get them out. Here is a video that shows the process step by step: