I really don't see your point. I have a small amount of whole milk in my black tea, mainly to aid in the cooling of it. In 4 litres, I'd probably be getting close to a cup of milk. So I would drink approximately 150 calories extra in a day, 13g of which would be carbohydrates consumed in a near balance with fats and proteins and due to the vast dilution would produce the minimalist of insulin responses.
So I really don't get your point. By drinking 4L of tea in a day, I would be consuming less than half the sugar of a can of soda.
Also Tea is hardly a mild stimulant, it contains more caffeine per unit than soda does. Yet people easily drink a few cups of coffee a day, which can easily have three-fold more caffeine than tea (five cups in a day would be close to 4L of tea) and have no ill effects from the caffeine unless they're caffeine sensitive and those people respond to decaf drinks with a tenth the caffeine in them.
So I really don't get your point. By drinking 4L of tea in a day, I would be consuming less than half the sugar of a can of soda.
Also Tea is hardly a mild stimulant, it contains more caffeine per unit than soda does. Yet people easily drink a few cups of coffee a day, which can easily have three-fold more caffeine than tea (five cups in a day would be close to 4L of tea) and have no ill effects from the caffeine unless they're caffeine sensitive and those people respond to decaf drinks with a tenth the caffeine in them.