Here's something else we noticed when we put our candy cane in oil and water.
A candy cane is full of tiny air bubbles (one reason the candy is white, not clear). When it dissolves in water, the air bubbles escape and float to the surface of the water. In this cup, the layer of oil traps the bubbles, slowing them down until they collect together and float to the surface.
(Full disclosure: a few of the bubbles in this cup were trapped there when we poured the oil in.)