The most commons uses of Simmons Insights are to create Demographic Profile of consumers of a particular product or to build a Cross Tab of data.
If you use Simmons to create a demographic profile, I suggest using [Data set] as the format, since "Demographic Profile" is in the title. The title of the data variable can be a bit convoluted, so just do the best that you can.
MRI Simmons. (n.d.) Demographic profile: Cold cereals- brnds eaten lst 7 days MO- Kellogg's Frosted Flakes (regular). Fall 2017 Adult Study 06-month. [Data set]. https://libguides.library.ohio.edu/business/databases/simmons-insights
If you cite a cross tab, there's really no ideal way to cite every variable that you use in the cross tab. I suggest just being as descriptive as possible without going overboard. Since the Cross Tab is the actual format, I put the entire description in brackets. For example, to cite the cross tab data used in my "How to Read Cross Tabs" example, I might do as follows:
MRI Simmons. (n.d.) [Cross tab of professional sports interest and family sit-down restaurants. Fall 2017 Adult Study 06-month]. https://libguides.library.ohio.edu/business/databases/simmons-insights