Like, for solid food, 50% sugar is what's typically in sweets, that means 50g sugar in 100g food. 10% sugar (that means 10g sugar in 100g liquid) is what's in sweet drinks like soda.

The WHO recommends restricting your sugar intake to a maximum of 10% of your calories intake. So for solid food that would be 10g sugar per 100g food, assuming the rest of the food is calorie-rich. For liquids it would be virtually 0g sugar per 100g liquid as liquids contain essentially no other calorie source.