Wipe the cables and tips before storing them and do the aforementioned cable-care steps. Also, if you know you sweat a lot and tendency is you might not use them the next day, stuff a small pack of silica gel in the pouch/case. Make sure you replace the silica pack once it changes color. Just make sure you buy one that does that, usually it's the ones in paper packets, but reseal the package where the paper packs come in otherwise they'll absorb moisture even before you use them.
If you already have something like the Pelican or Otterbox cases, use that to store them at home (still with the gel packs) and keep the nylon case or cloth pouch for when you take it out of the house. When you get home just transfer to the plastic water-tight case. I won't recommend buying one unless you already have it or the IEMs came with one though, since those cheap silica packs aren't likely to absorb enough moisture in the fabric pouch/case to catch up to the cost of a Pelican. A small Lock and Lock container would do, but you might find it a little ghetto since it looks too much like it should have food in it, but I use the large one for my camera.