Fructose induces insulin resistance. I had read a paper that compared several fructose concentrations in drinking water of low -dose Stz rat model, but I don't have the link.

You may check these for details:

https://www.omicsonline.org/open-access/the-role-of-fructose-in-type-2-diabetes-and-other-metabolic-diseases-2155-9600-1000659-98130.html

https://www.nature.com/articles/s41598-017-18896-5

Thanks @ Dr Ibrahim

to avoid hypoglycemic shock due to b-cell distraction by streptozotocin so insulin release in high amount to blood.

Thank you @ Dr Jarad

I recommend that you have a look at the SOP from the University of Melbourne:

https://staff.unimelb.edu.au/__data/assets/pdf_file/0007/1974346/STANDARD-Streptozotocin-use-in-mice-and-rats-FINAL.pdf