If you’re playing the same games they play on the label, sure. There is less than one calorie per serving.

(Edit: in Diet Coke. Not too sure about Coke Zero).

What game is played? To me it seems pretty straightforward that for both the actual caloric content is ~0.

I believe it’s .4 calories per serving which is less than one and which rounds down to zero, but it’s not approximately zero by a long shot.

How is 0.4 kcal "not approximately zero by a long shot"?

Especially when compared to a standard coke with around 150 kcal.

Well, it’s almost half a calorie, to begin with.

By the time I finish the can I'll have Burned through more than 0.4 calories.

0 × 10 = 0

...that's the joke.