UPDATE:

"Brazilian fact-checker Aos Fatos and Estado Verifica found that a car would need to reach an internal temperature above 300 degrees Celsius (572 degrees Fahrenheit) to cause hand sanitizer to combust. A study by Arizona State University looking at cars parked in triple-digit summer heat found temperatures topped out around 160 F (71.11 C)," according to its report.

Most hand sanitizers are alcohol-based and therefore flammable - you should not leave them in your car, especially on hot days. You should also not leave clear water bottles in the car because the sun rays can hit the plastic and start a fire.

Western Lake Fire Disctrict shared on their Facebook page:

We’ve chatted in the past about clear water bottles being kept in your vehicle when the weather is warm.

That still holds true and so does hand sanitizer! By its nature, most hand sanitizer is alcohol-based and therefore flammable. Keeping it in your car during hot weather, exposing it to sun causing magnification of light through the bottle,
----and particularly being next to open flame while smoking in vehicles or grilling while enjoying this weekend----can lead to disaster.

The car door fire picture is from Brazil after hand sanitizer contacted open flame.

Better not to smoke at all of course.