I came across this article on a website created by two US academics who teach a course on spotting fake news. No one is suggesting that Nestle is lying on the package – the statistic used is true, but it is also meaningless.
"99.9% caffeine-free," the packaging boasts. That night at the hotel, a 99.9% caffeine-free drink seemed like a good idea to me, a prudent alternative to an evening cup of coffee given that I was already chronologically disposed to stay up until bedtime three time zones to the west.
But pause and think about it for a minute. Caffeine is a really strong drug, after all. And there's a lot of mass in a cup of cocoa. Caffeine in coffee is not like sugar in coke, for example. So is a 99.9% caffeine-free drink really something you want to drink right before bed?
Let's figure it out. How much caffeine is in a cup of coffee? According to the Center for Science in the Public Interest, there are 415 milligrams of caffeine in a 20oz Starbucks coffee. (This turns out to be on the strong side relative to other drip coffees or milk-based espresso drinks.) That corresponds to about 21 mg of caffeine per ounce. An ounce of water weighs about 28 grams. Thus a Starbucks drip coffee is about 0.075% caffeine by weight. In other words, strong coffee is also 99.9% caffeine free!
While I don't have an exact figure for this brand of cocoa, most cocoas have about 20mg of caffeine in a 8 ounce cup, i.e., they're about 0.009% caffeine by weight. At first I thought that perhaps the 99.9% figure referred to the powder, not the finished drink. Given the figures about, the powder probably is close to 0.1% caffeine by weight. But Nestle's website makes it clear that they are referring to the prepared drink, not the powder: "With rich chocolate flavor and only 20 calories per single-serve packet, this cocoa makes a 99.9% caffeine-free, 8 fl oz serving."
Thus it seems to me that Nestle's packaging could list an extra decimal place: 99.99% caffeine free. So while there's nothing inaccurate or dangerous about the 99.9% assertion, it's a kind of silly thing to say and an even sillier thing for us to be reassured by. Most regular coffees could be labeled in the exact same way.