If the only way you would drink green tea is with the sweetened variety, then overall it would be healthier for you to stick with the added sugar (though your taste buds would probably adapt to the unsweetened variety, or you could try adding a harmless noncaloric sweetener such as erythritol (see A Harmless Artificial Sweetener). (nutritionfacts.org)
Studies on calorie restriction through short - term fasting just before chemotherapy — defined as a complete lack of food and caloric beverages (noncaloric beverages such as water are allowed) for 72 hours or less — has demonstrated a wide range of beneficial effects. (rdlounge.com)
Sugar alcohols aren't considered noncaloric or non-nutritive sweeteners because they contain calories. (mayoclinic.org)