Water. We all know we're supposed to drink it. Our parents, doctors, teachers have told us our whole lives: drink 8 glasses a day. Did you know your body, which is 60-70% water, needs 64 ounces of water per day? It doesn't want it, it needs it. Did you know it helps circulation, digestion, concentration, energy levels, complexion and diet? And no, coffee, caffeinated tea, juice, soda, alcohol, and milk don't count.
So get going! Fill up that bottle or glass and drink drink drink all day long. You'll feel better, trust me.
(disclaimer: this does not apply to babies - breastmilk, formula and milk - that's what the little guys need)