I do not take pills with water, but I have found that water, Emergen-C, and oral rehydration fluid do help in some cases, and I highly recommend them.
As far as I can tell, dehydration is a contributing cause to my headaches, but not the primary cause. Unsurprisingly, liquids help the most after I have been exercising.
Very interesting decision from the one of the leading scientific publications to publish an article about Reiki therapy.
http://www.nature.com/news/consider-all-the-evidence-on-alternative-therapies-1.18547
[Edit: should be Nature publishes an article about alternative therapy]