There is no hard number as to the cups a day for fluids. Basically, if you are thirsty, drink as that's an indication that you are dehydrated. Different people need different amounts and you do get fluid through food as well. I find for me personally, I drink maybe a cup of fluid the entire day until 5 or 6pm then I drink like 5 or 6 glasses in a 2 hour stretch. I don't know why but that's how I am.