We have found evidence of the range of substitutes that housewives were advised to use in place of sugar when preparing fruit jams and preserves. Alternatives included glucose, salt and benzoate of soda. These were not always entirely successful, as can be seen in this news article from August 1916.
WARNING TO HOUSEWIVES
Communications have reached the Board Agriculture and Fisheries referring to a statement which has appeared in the public Press to the effect that benzoate of soda may be used to replace sugar in the preparation of jam. The Board are advised that benzoate of soda is quite unsuitable for the purpose in question, and desire to warn the public against its use in jam making. Serious results might follow an tempt to substitute this material for sugar.
Benzoate of soda (more commonly known now as Sodium Benzoate or E211) is indeed a food preservative, still used today. However, it has to be used carefully, since contemporary research has revealed that sodium benzoate can cause or increase symptoms of gastric, nervous and respiratory disorders and ADHD or hyperactivity in children. To top it all, when mixed with ascorbic acid (Vitamin C), it transforms into benzene, a known carcinogen – generally not a good thing to find in jam.
Fortunately for the children, there was clearly still enough sugar to make toffees!