True, but your body only produces 0.5 liters (~17 fl oz) over a 24 hour period, and has 0.15 liters (~5 fl oz) at any one moment. So, being well hydrated when s

True, but your body only produces 0.5 liters (~17 fl oz) over a 24 hour period, and has 0.15 liters (~5 fl oz) at any one moment. So, being well hydrated when sleeping might positively affect other systems, but the effect on your CSF would be negligible.