I have found an easy way to actually take a blood sugar on your manikin.
Soak a very small piece of gauze in the control liquid from your glucometer. Put this gauze on your manikin's finger and cover with tegaderm. Students can stick the gauze with the lancet and squeeze out a drop of fluid onto the glucometer strip. I have tried putting a drop of blood concentrate on the gauze to make it more believable, but it is very messy and dilutes the control liquid. Good luck!