Rent your space for storage
What about offering the space for boat and RV parking/storage or even putting in portable storage pods? Here's a link to the National Portable Storage Association to start your exploration around that idea.
Host food fairs and carnivals
Many state and county fairs and festivals of all kinds have been canceled. That means those vendors need a place to sell their fried candy bars, elephant ears, and other delicacies. They're looking for solutions, too, and they're used to setting up in parking lots. Here's a link to carnival and amusement industry directories.
You could also work with local organizations to provide space for health fairs and other community gatherings, although that would seem limiting as far as income. It would bring folks into your parking lot, though, and close to the businesses that are open there while generating goodwill.
Host a food truck rodeo
Food trucks are now a thing, not a fad. Consider having a food truck rodeo, lining up as many as would comfortably fit your space and local authorities would permit at this time. Here's a link to a site that specializes in them.
Temporary fixes in unpredictable times
These temporary fixes won't replace the business from tenants who hopefully will be soon thriving again and need that parking for customers and employees, but they can help create some cool cash over the coming weeks and months.
Be realistic about how much income your parking lot can generate and allocate your time and resources accordingly, and the effort could well be worth it now and going forward into who knows what lies ahead.