How does a cup of tea with 2-3 cubes of sugar affect the body? What if I drink 5 cups of tea with sugar? What are the disadvantages?
To help put it in perspective:
Your average 8oz cup of tea contains 26mg of caffeine; about the same as a 12oz can of soda, which contains 29mg of caffeine.
3 sugar cubes is about 7g of sugar (27 cals), while a can of soda has about 33g of sugar (138 cals).
So, 5 cups of tea with 3 cubes of sugar each would be about the equivalent of a single can of soda's worth of sugar and 5 cans of sodas' worth of caffeine.
It's generally recommended that you eat no more than 25g of added-sugar per day (or 5% of your daily caloric intake, whichever comes first), but it's best to limit it as much as possible. High blood sugar will cause insulin spikes which can cause your body to store extra fat and prevent muscle gain.
The best time to consume sugar is after a workout, since it helps restore glycogen levels. It also helps optimize the absorption of creatine if you take supplements.
A single cup of tea with 2-3 sugar cubes after a workout should be relatively harmless and may even help your recovery, but if you're going to be drinking a lot of tea throughout the day, I would recommend using less sweetener or calorie-free sweeteners such as stevia (i.e., Truvia).
On the contrary, if you're trying to lose weight, a cup of tea (preferably green tea with no added sugar) right BEFORE your workout is shown to raise your metabolism and aide in fat-burn.