Roll out a ½-inch-thick layer of air-drying modelling clay.
Lubricate the clay with some cooking spray. This will allow the bottle (around which you will mold the clay) to be easily removed.
Place a regular glass bottle onto the clay sheet and mold the clay around it. The mold only needs to cover half the bottle.
Repeat the steps above to create the second half of the mold.
Leave the clay to dry for at least 24 hours with the bottle still inside and remove the bottle just before adding the sugar glass mixture.
Mix 2 cups of water with 1 cup of corn syrup, 3½ cups of sugar and ¼ teaspoon of cream of tartar in the cooking pot. This makes clear sugar glass, but green or brown food coloring can be added to the mixture.
Bring this mixture to a boil slowly so the sugar does not caramelize. Keep an eye on the temperature of the liquid and do not leave unattended.
Remove the sugar glass from the heat when it reaches 300 degrees Fahrenheit (150 degrees Celsius) and pour straight into the mold to cool. Lubricate the mold with cooking spray before pouring in the sugar glass.
Leave the sugar to solidify. This will take at least 1 hour depending on the thickness of the glass.
Glue the two halves of the mold together and stick on a fake label. Make the glass a couple of days in advance and keep in the refrigerator until needed.