Mostly everyone now carries hand sanitizer everywhere they go. There are plenty of different products available from gels, liquid, or spray. The recommended concentration of Ethanol Alcohol is 60% and more is better.
So is it safe to keep hand sanitizer inside your car in the Miami sun? The short answer is YES, it is. The reason is simply that alcohol will keep its potency unless one of two things happen: 1. it evaporates and 2. it burns up. As you know, alcohol evaporates very quickly in the open air.
Don’t worry, your hand sanitizer WILL NOT catch fire. It will need to reach somewhere between 300- and 500 degrees inherent for it to actually combust according to The Poynter Institute and while the inside of your car can get very hot (about 160 degrees), it is not hot enough to catch fire or cause the alcohol to burn out.
For those of you that are cooks, you know cooking wine is used in some dishes and the alcohol eventually burns out. You need a temperature of at least 172 degrees for alcohol to burn off so your car will get pretty close but unlikely. Although the flash point of 70% Ethanol Alcohol is 17°C (63°F), if your hand sanitizer bottle is tightly sealed or better yet, made of glass, again, it is unlikely to burn off or catch fire.
In the end, it is your choice to leave hand sanitizer in your car or not but it is a very good chance, that it is safe to do so!
Flash point referencePoynter Reference