Water is ESSENTIAL to everything as oil is to the engine in your car. Did you know water is actually a part of what causes your neurons to fire effectively?
For things to get built in your body and brain? Think of your hundred billion (or less) brain cells/neurons and trillions of molecules and networks of molecules in your body as independent workers and entire companies that churn out a product- and all having to, themselves drink the equivalent of 8 glasses of water each day and throughout (scale down to their size vs the 8 oz glass you yourself would drink- so each water molecule you introduce is like the rain in a drought!
If your not drinking enough water think of it like how it doesn't rain in many parts of the world and crops die, all hell breaks loose and people start to do dances and pray, even try to extract water out of the air- well your molecules tend to do the same thing and the damage inflicted is what causes your mood loss, your body aches, disease, and the inability to grow new crops of dopamine, cell membranes, and even those powerful networks that create your libido!
Be the "god" of your body that makes it rain and saves the crops, saves the cells, saves the networks and even entire "companies" of cells that do very important things. Imagine if a company got a nice shipment of precursors to building things but without the water to give the workers and they can't bring any because other more vital companies like the red cross- took it, how would they work? How would they even survive?
Water is more important than even food although water is what makes food work and break down, and keeps your body alive.
Without nutrients and water even minerals found in tap water (and often missing from bottled water!), the body can't function effectively thus waking up in an uphill groggy and tired fashion everyday is often due to this problem. Processed foods and most fruits and vegetables in the grocery store not marked "organic" are likely useless.
Processed foods are stripped of their nutrients in the processing, cooking, and/or the preservative additives (that dissolve them), and vegetables not marked specifically "organic" are likely grown in bad soil void of nutrients and vital nutrition for the plant to convert into vitamins!
Supplements can and often need to be taken with food to assure you get all your nutrients- we'll cover this in the next section as it relates to both body and especially brain chemistry.