What You Did
You attempted to diffract sunlight into its different wavelengths using a glass of water as a prism.
At certain angles, the glass of water should have projected a small image of a rainbow onto the sheet of paper.
You may have tried this experiment at the wrong time of day to catch the rays just right, or you may not have tried enough angles to get the intended result.
Try this experiment at different times of day, or different times of year. Try with a clear plastic cup or a clear cup of a different color. Just make sure it's clear so that the light will go through it and the water.Try with different colors of paper