The “8 glasses” rule survives mainly because it’s easy to remember and makes water-bottle companies very happy. In reality, your body adjusts hydration based on need, not a magic number from 1945. Thirst already works as a built-in notification system — no app required. And yes, coffee, tea, and soups all count. Unless you’re trekking the Sahara, you can relax: hydration isn’t a math exam.
