Here's another with a bit more information:

http://www.sugarstacks.com/beverages.htm

In looking over the science project, I think it has an error. Coke reportedly has 39 g of sugar in it. With a density of 1.59 g/cm³, that's 24.5 cm³ of sucrose. And, with 5.0 cm³ per teaspoon, that yields 4.9 tsp of sugar, not the 11 tsp indicated on the display.

Am I wrong?

(The density of 1.59 g/cm³ assumes the sugar is being reported as sucrose. High fructose corn syrup is about 50% fructose with a density of 1.69 g/cm³ and 50% glucose with a density 1.54 g/cm³, or about 1.61 g/cm³ total sugars. That would change my resulting volume to 4.8 tsp instead of 4.9 tsp).

"How did you determine how much sugar to put in the bag?"

"The label says 39 g of sugar, so I weighed it out."

End of story.

Getting back to the lazy man's approach: From what I can gather online, a teaspoon of sugar (5 cm³) weighs about 4 g, or a bulk density of 0.8. So, 39 g of sugar would have a volume of 9.75 tsp, which is pretty close to the 11 tsp on the poster. The size and shape of the sugar granules will determine the bulk density, and this varies. Close enough.

I stand corrected.