Hyponatremia. The Inquisition was forbidden from drawing blood during torture. A gallon of water forced down your pie hole was very effective for stimulating compliance.

http://www.mazepath.com/uncleal/homesec.jpg

Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/qz3.pdf