Which chocolate has the least sugar

For dark chocolate, the sugar content is close to 100 minus the cocoa percentage. A 70% bar is roughly 30% sugar; an 85% bar roughly 15%; a 100% bar none at all.

Milk and white chocolate break the rule, because their remainder includes milk solids as well as sugar. A 35% milk chocolate is not 65% sugar — closer to 45%, with the balance being dairy.

So within dark chocolate the ranking is simply the percentage, and the practical low-sugar choices are 85% and above.

Polyol-sweetened chocolate genuinely contains little or no sugar, and it contains essentially the same energy, because cocoa butter rather than sugar is the main contributor.

If the goal is less sugar, it works. If the goal is fewer calories, it does not, and the premium buys very little. Maltitol also has a laxative effect at quantities people routinely eat in one sitting.

For most people the useful move is a higher percentage rather than a sugar-free product: an 85% bar delivers roughly half the sugar of a 70% one, tastes of considerably more than a polyol-sweetened bar, and costs less.

Unsweetened 100% chocolate has none at all and is an ingredient rather than something to eat, which is worth knowing before buying it for that reason.