Originally Posted by WizardOfBoz

A banana and water. Worked for Gino Bartali.

If you are having cramps and stuff, pre-hydrate. Have your Doc check your vitamin D level.

If you have the flu and can't keep anything down, pedialyte may be helpful. But as Skipjacks says, it's expensive and doesn't taste so great. Better, better tasting, and cheaper options abound.