When you’re well hydrated you should feel more energetic, stronger when you’re upright and walking, able to go from sitting or lying to standing without getting dizzy and feeling like you’re gonna pass out. Dehydration makes one feel weak, sluggish, headachy ,constipated , and just drained in general. It can also raise your heart rate, make your blood thicker and more prone to clotting and its bad for your kidneys. I add a squirt of a zero sugar, no calorie flavor enhancing liquid that comes in a small plastic bottle from grocery. Many flavors, non carbonated, about $2.50. It turns the water a pretty color as well as making it taste good.