Why drinking fluids don't compensate the need of water(for e.g:if i drink a cup of unsweetened tea,the need of water through the day don't decrease?)?

Caffeine: Tea and coffee and many carbonated drinks have caffeine. Caffeine increases the excretion of water by the kidneys and you need to make up for that loss. For good health - Have a diet rich in fresh vegetables, fruits, whole grains, milk and milk products, nuts, beans, legumes, lentils and small amounts of lean meats. Avoid saturated fats. Drink enough water daily, so that your urine is mostly colorless. Exercise at least 150 minutes/week and increase the intensity of exercise gradually. Do not use tobacco, alcohol, weed or street drugs in any form. Practice safe sex, if you have sex.

Unsweet tea = fluids: Tea, coffee and soda do qualify as fluids for your body , and it is recommended that adults drink at least 6-8 cups daily. Water is preferred, as it doesn't have chemicals like caffeine or sugars that require extra metabolism or extra calories. Fluid intake should be enough to relieve all thirst and to allow a person to urinate 4-5 times daily with urine that is very light yellow.