[Leaning Right]

> a garden bucket with water from the kettle and three bags of sugar <

Adding the sugar increases the boiling point of the water, and so makes the water hotter (it will reach a higher temperature before it starts to boil). I wonder how she knew that.

[Michael.SF.]

She may not have known about the boiling point, but, the recipe of water and sugar is how you make simple syrup, which in turn can be a viscus and a bit sticky of a substance. It is more likely it was that which was on her mind, knowing it would make him suffer more.

[Mom MD]

some of us remember basic chemistry

[Valpal1]

Anyone who has made jellies, jams and simple hard candies knows this.

It’s also in the basic how to section of any halfway decent cookbook. And it was taught in home ec classes.

[zeugma]

Adding the sugar increases the boiling point of the water, and so makes the water hotter (it will reach a higher temperature before it starts to boil). I wonder how she knew that.

Salt would have the same effect. I don't know which would allow for a higher boiling point.