Since a cup of brewed tea only has 2 calories, the number of calories in a cup of tea that is sweetened with sugar will be largely dependent on the amount of sugar that is added to the cup. A heaping teaspoon of granulated sugar has 23 calories, so a cup of tea with a teaspoon of granulated sugar will have roughly 25 calories. The calorie count increases as more sugar is added to the tea.
Tea is a beverage that is traditionally made by steeping leaves of the Camellia sinensis plant that is endemic to the Asian continent. This beverage is believed to have been consumed in China as a medicinal potion with the earliest records of tea dating back to the 10th century B.C. Tea was introduced to the West by European explorers and merchants in the 1500s, where drinking it became a fashionable trend among the British in the 1600s.
Sugar is not the only tea additive that can add to the calories in tea. Milk is also a traditional tea additive that can add more calories to a serving of tea. Other common tea additives, such as liquid honey or honey drop, fruit jams, agave nectar, mint, butter, and sometimes whiskey or brandy in tea-based cocktails, will also affect the number of calories in the beverage.