I believe night cramps or leg cramps are caused by insufficient fluid in the vascular system. The fastest solution I know is to drink 1 to 2 ounces of 5% vinegar in an 8 ounce glass filled with water. Cramps will be gone in less than 2 minutes. If you simply guzzle 8 to 16 ounces of water it seems to take 5 to 10 minutes. My wife preferred for me to squeeze 3 large limes in place of the vinegar and add sweetener.
Background: the wives tale about waiting 30 minutes after eating to go swimming to prevent cramping. My thought was that food made the digestive tract go basic. Hence making the digestive tract go acidic will reverse the process and send fluid to the vascular system. I am not a doctor and don't claim this will work for everyone, but my wife and I have done it for years. More background is the use of pickle juice by high school football coaches when players start cramping during training in the heat of summer. If this doesn't work please see a doctor about vascular insufficiency. My personal ailment is hyperaldosteronism; I flush potassium, hence my cramps (and fluid issues) are caused by electrolyte issues.