Hydration is more complex than you think. In general, plain water is what you need to drink for hydration. It’s better than soft drinks, including “diet,” with too much sugar and too many chemicals. Fruit juice is better but only if it’s really fresh. And too much coffee can dehydrate you.
6-8 glasses of water a day are recommended.
Skin is an organ!
It’s true that the very outer layer of the skin doesn’t get very hydrated, but that’s because it’s getting ready to shed. It is also true that sleep is extremely important for hydration. During sleep, the water in our bodies re-equilibrates, and the fluid that collects in our legs during the day, flows back when we lie down, to our faces. Think reversing gravity!
Healthy oils like olive oil, avocado oil, nut oil, etc don’t “hydrate” skin but they do supply the oils that are building blocks for the fats naturally present in skin, and help keep it healthy and pliable. They make skin look more hydrated.
Dr. Irwin’s short article on moisturizers