How to keep sugar coating from dissolving and turning to surup?

I like to do a second dredging in sugar, just to make sure. Then when I store in an airtight container, I add little extra sugar to absorb any moisture (sugar is hygroscopic; loves to suck up water). If you live in a climate with high humidity, it might make sense to put in a food-safe desiccant pack to the container to control the moisture. Hope that helps.