Part of the point of fasting is to lower insulin levels. Injecting yourself with fructose is kind of contrary to the idea.
But If you are getting the shakes after not eating for a number of hours, this could be an indicator of hypoglycemia, in which case you should probably monitor your blood sugar levels and maybe work up to longer fasts over a more extended period of time.
Breaking fasts with sugar isn’t something I would recommend. If you need to eat something, bone broth is a better choice.
Aside from that… eating is not fasting. But, you do you. People fast for different reasons and come up with ways that work for them.