Thermoses have gotten kind of amazing these days. Have you noticed? The best double-walled, vacuum-insulated travel mugs can keep your coffee hot literally all day. I've left my Fellow Carter Move mug ( see on Amazon) in a car for hours while hitting the farmers market and meeting a friend for lunch, only to discover my coffee still bracingly hot and tasting pretty much the same as when I brewed it. It feels like a miracle.
After that, I was hooked. Despite having a shelf full of insulated water cups and travel mugs of every shape and size, I still can't resist wandering down the tumbler aisle at my local sporting goods store or T.J. Maxx. Speaking from experience, although it seems like these are items you can buy without a second thought, doing so is a big mistake.