My wife takes her Hydroflask everywhere, but it won't fit in the cup holder of the car, so I made this for her. I included an optional bottom panel if you need to put a smaller cup in it that would fall to the bottom. The panel can also be fitted with a .5" magnet, if needed. It makes a secret compartment (just not for your extra car keys).

Side note, this model has been made in direct competition to @Lins model https://makerworld.com/en/models/481861#profileId-393747 .@Lins is a great new designer, who blew me away with his model when I asked him to make one for me. He is brand new to 3D modeling and I'm sure will surpass anything I make in a couple months, lol.