The number of grams present in a teaspoon depends on what is being measured. Different substances provide different results.
A gram is a metric measurement of weight. A teaspoon is a measurement of volume. Therefore, the number of grams that comprise a teaspoon varies depending on the substance being measured. For instance, 1 teaspoon of water weighs 5 grams. One teaspoon of sugar weighs slightly less at 4 grams.
According to the United States Department of Agriculture, there are 33 grams of sugar in a typical 12-ounce can of cola. This equals 8 1/4 teaspoons of sugar. A 12-ounce can of Coca-Cola contains 39 grams of sugar or 9 3/4 teaspoons.