Well, more specific than "clothing", I've gotten the idea in my head that a button up top that could be worn open over other tops would be a great thing to keep in my car for unexpected times outside. I keep a sunhat but since I'm often sleeveless in the summer a shirt I could wear on top seems like a good idea.
My first idea was a linen "big shirt" and that should be easy to come by. But linen is hardly sun protective. Better than nothing...and maybe good enough since sun time is not something I seek out. But actual protective tech would be ideal if there is a kind that is breathable and cool. And not anything like a surf shirt...I want to be able to put it on over whatever I'm wearing. Does such a thing exist? I saw a FB ad that triggered this thinking, but the shirts were sheer so I'm skeptical.