New studies found that drinking seven glasses of water can cure headache and migraines. This is a placebo effect of water but found to be comparatively effective against pills.

At the end of the study, patients filled a questionnaire named the Migraine-Specific Quality of Life index to express what changes they felt. The results were published in the journal named ‘Family Practice’, which showed that those who drank extra water showed a significant relief from headache.
The researchers said that they suspect that some patients may benefit from drinking water and it seems reasonable to recommend they try drinking more for a short period of time and see if they experience any kind of improvement.
Dr. Fayyaz Ahmed of the Migraine Trust, said that the benefits of drinking water during headaches and migraine could be due to placebo effect, i.e. no known medical effect of water is known on headaches and migraine. But in the end he added that regular intake of water and adequately hydrating is a healthy option and our body benefits from it in many ways.
Sources: http://psychology.about.com/od/pindex/f/placebo-effect.htm
Source-Medindia