I've had a couple of those little 12v coolers, they draw 2-3A continuous and a 1.8W battery tender / 12v is 150mA. If you bought over a dozen of those battery tenders and paralleled them and had perfect sunlight and a small cooler it would work.

I used it when my wife had to take insulin shots. I bought the second battery tray for the diesel model of my truck and put in a second battery and isolator and had the cooler running off the second battery.