I have an empty water bottle at work and when there’s left over coffee I’ll throw some into one of those water bottles (sometimes I mix in sugar and creamer, sometimes I do this after) so that the water bottle is about half-full or less.
I lay the water bottle on it’s side in the freezer so the coffee is at an angle and lies along the side of the bottle but doesn’t cover up the mouth of the water bottle. Then the next day I’ll pour hot coffee directly in the water bottle and sometimes add sugar and creamer. Screw the lid back on, shake it throughly, then drink. I admit it’s not very elegant looking but it’s tasty and easy. The frozen coffee gives you ice without diluting the coffee by adding ice made from water. I came up with this because somebody had once told me that they made ice cubes from whatever drink they were drinking (not sure if it was an alcohol based drink or not) because then the ice didn’t dilute their drink. I didn’t realize until that point why somebody would make plastic ice cubes, but that explained it.