How many calories are in a 12 oz can of Coca-Cola?

How to get close to this number

Go through the sugar. The drink is essentially water, flavouring and sugar, and sugar carries four calories per gram. If you know roughly how much sugar is in a can — and the explanation puts it near ten teaspoons — then multiplying gives the calorie count almost exactly. Reasoning through a single macronutrient is the cleanest possible route for a food with only one.

The framing that lands is the teaspoon count rather than the gram count. Thirty-nine grams is abstract; ten teaspoons is a quantity you can picture being spooned into a glass, and almost nobody would add that voluntarily. Converting a mass into a familiar physical unit is the most effective way to make a nutrition figure mean something.

The health comparison in the explanation is the one with teeth: a single can exceeds the entire daily added-sugar guideline for an adult. That is why sugar-sweetened drinks get singled out in public health policy rather than treated like any other food — the calories arrive in liquid form, which produces much less satiety than the same energy eaten, so they tend to be added to a day's intake rather than displacing anything.