Yes, it’s kind of a silly idea. Would probably go with a propane stove instead. To run a microwave would require several thousand in gear, including Li batteries, B-to-B charger, inverter, etc. Plus $800+ for a fridge. That same money buys a lot of burritos and sandwiches.Microwave is going to be tricky, given the rated output of the on-board inverter.
Adding a standalone LiFePO4 based inverter+battery bank feeding the microwave oven would be more viable, letting the bank (re)charge off the vehicle on-board source (either 12VDC or 120 VAC/400W).