I'm confused! Are you doing a project based on this idea: http://www.sciencebuddies.org/science-fair-projects/project_ideas/HumBeh_p016.shtml
If you are basing your project on that kind of an investigation, there are lots of issue with running that kind of an experiment. READ THE CONCENT aspects and needing to get the project cleared with your Science Fair rules folks.
Without knowing what your hypothesis is, it would be hard to determine what if anything should be used as a control group.
Depending on your hypothesis and your experimental proceedure, the control group might not even be a medicine or candy, it might be a group of people, say some pharmacists professionally trained in identification of medicines.
In terms of pills looking extremely similar to some candies, a red 30 mg Pseudoephedrine tablet looks a lot like a round red hot candy once they are out of the packages.
There are some excellent materials available starting on the Science Fair Project Guide page that deal with the scientific method and possible ways of dealing with its different aspects including coming up with a testable hypothesis.