2. 1 Gallon a Day

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The amount of water you are supposed to drink every day is currently under great debate, as we draw far more from food than previously thought, plus we actually generate water, which means some of our urine is not related directly to the amount we drink. However, it is fair to say that a lack of adequate hydration causes problems ranging from poor energy levels to wrinkles, therefore this app is handy to have around to track how much water you take in.