“A green smoothie a day is probably the most incredible thing you can do to hydrate yourself,” Cohen remarks. That’s because all those greens (spinach, kale, what have you) contain significant amounts of fiber, which helps you hold on to water much better. “The fiber is what really acts as a sponge,” Cohen notes. 

More hard data is needed, she adds, but her anecdotal evidence speaks volumes: In Cohen’s practice, patients who incorporate a green smoothie into their daily regimen feel way more hydrated. “[I have] patients who say, ‘I drink so much water all day but I can’t quench my thirst.’ And I have them add a green smoothie or two a day, and it changes everything,” she recounts. 

Cohen’s own morning sip includes a handful of greens, half an apple (“an apple and a bottle of water is more hydrating than two bottles of water,” she notes), some lemon, and a knob of ginger, but you can learn how to create your own concoction here

https://www.mindbodygreen.com/articles/tips-to-stay-hydrated-without-chugging-water