Pop quiz.

Three coffee orders. One glucose monitor. Only one of them wrecked me.

Black coffee. A latte. A caramel frappuccino.

I drank each one on a separate morning, same time, same empty stomach, and let my glucose monitor catch every bit of it. Guess which drink barely moved me. Then guess which one nearly matched a slice of cake.

Here's the twist. It's not only about sugar. Caffeine on its own can nudge your blood sugar around, even in a cup with nothing else in it. So this isn't as simple as "no sugar, no rise."

Take your guess. Then scroll for the reveal.

● The Reveal

The frappuccino wins. It's not close.

Eighty-two points. That's higher than a lot of desserts land on my glucose monitor.

Here's why. A grande caramel frappuccino carries somewhere between 54 and 66 grams of sugar, depending on the size and the whipped cream. That's more sugar than a full can of Coke. In other words, you're drinking a milkshake that happens to have coffee in it.

The latte barely moved me. It has about 18 grams of carbs, and almost all of that is lactose, the natural sugar in milk. Milk sugar digests slowly because it arrives bundled with protein and fat. In other words, the protein and fat in the milk act like a brake on how fast your body absorbs the sugar.

Black coffee was the real surprise. No sugar at all, but still a small rise. Caffeine on its own can make your body slightly less responsive to insulin for an hour or two. That's a real, measured effect in research on caffeine and insulin sensitivity. It's small, and it doesn't need any sugar to happen.