Add the cement mix to a bucket, and stir in water. Youll need 4 parts cement to 1 part water. Mix well.
Spray the inside of a mailing tube with cooking spray.
Then, start pouring the concrete mixture into the mailing tube. Only fill about halfway.
Place the juice glass inside the mailing tube, pressing down so that the concrete starts to push upwards, surrounding the sides of the glass. If more concrete mixture is needed, spoon it into the mailing tube, in between the sides and the juice glass.
Wait for the concrete to dry. If you're using a rapid setting concrete, it should be completely dry in 3-5 hours (depending on the temperature, etc).
Once dry, rip the container away to reveal your new vase.