Do clinical trials use sugar pills?

Almost never, though there are select situations in which there is no clearly defined standard of care for which no treatment has been proven to be effective. In this situation, participants could be randomized to a new treatment versus a placebo. 

Generally, phase III clinical trials randomize patients to a standard of care, newer treatment, or standard of care plus a newer treatment. 

Most modern clinical trials do not treat patients with a placebo.