I just bought a thermos called the Stanley Classic One Hand Vacuum Mug.
The main reason is that it's the only thermos I'm aware of that both fits in a standard car cup holder, and also has a mouth wide enough to accommodate my Aeropress coffee maker. The Aeropress fits well enough in the top, which means I can make coffee directly into the thermos.
These sound like insignificant features, but for me, they're very important. As we travel around the world, we stay in arbitrary housing, often AirBnB houses, apartments or even rooms. These usually have kitchens with all the trimmings. But sometimes they don't. I find myself having to make my own coffee using whatever equipment I brought with me. It's really great to be able to make coffee directly into a thermos, which I can then take. Without the direct brewing, I would have to find some other vessel to make the coffee in, then somehow transfer it without spilling.
We often rent a car to drive around and explore. It's usually hard to find a reasonable place to get coffee, and it can be time-consuming to park. Coffee can be expensive to buy. Many countries don't have the culture of taking coffee "to go." And American-style drive-thru windows are exceedingly rare abroad. As a result of all this, a simple cup of coffee can require 15 minutes finding parking, a 10 minute walk, a 15 minute wait for the waiter, followed by another 15 minutes for the coffee. Because one weak shot of espresso doesn't cut it (I am a writer, after all), it often costs more than $6 or $8 for the coffee, plus a tip. Then, another 10 minute slog back to the car.
Amira doesn't drink coffee. So I'm not only enduring this, but imposing it all on her.
A thermos that enables me to make coffee directly into the thermos, then have hot coffee with me all day saves big time and money.
Stanley thermi are pretty good quality, but not the best. For example, the Zojirushi SM-KHE48AG Stainless Steel Mug is higher quality from a materials and fit-and-finish point of view.
Their abilities to retain heat are comparable.
The Stanley thermos is a beast; the kind of thing that might be used by a building contractor who drives a Ford F-150 pickup truck. The Zojirushi is the kind of thermos that might be used by a financial analyst who drives an Infiniti Q50 sedan.
But while the Zojirushi and many other such products do fit in cup holders, they don't allow making coffee directly into the thermos with an Aeropress. And that's a deal-breaker.
With the Stanley full of coffee, and the lid on, you can turn it upside down and shake, and literally zero drops of coffee comes out. You press and hold the button at the back while taking a drink. When you let go, and turn it upside down again, zero coffee drips out. You can drop it, throw it and do anything with it, and no coffee gets spilled. It's pretty amazing.
I've not only bought this thermos, but added it to my list of gear on the Gastronomad Gear page. I highly recommend this product to anyone who uses an Aeropress.