Get a spoon or equivalent object, put the coke on it with a pinch of baking soda. I can't tell you exactly how much because it depends on the amount of coke and shit, you can always put more later. Add some water to the spoon and mix while heating underneath with a lighter (or candle). You should notice a chemical reaction taking place and can add baking soda until it appears to have stopped or the water has evaporpated. The rocks sould be on the top, cuts on the bottom.