The recommendation of drinking 8 glasses of water has no medical reasoning. The current advice is listening to your body and drinking when thirsty, unless you're outside on a hot day.
https://healthblog.uofmhealth.org/womens-health/myth-busting-no-more-8-glasses-a-day
https://healthblog.uofmhealth.org/womens-health/myth-busting-no-more-8-glasses-a-day
