I don't do a lot of caulking but when I do the nozzles on my used tubes seem to always be clogged. Caps don't work, short plugs don't work, etc. The only thing I find that works for me are large long nails that I put into the end of the nozzle that extend down into the tube. My issue is that over time my nails tend to rust. I then end up waisting a significant amount of caulk each time just to get the rust infested part out of the tube.
These caulk tube "nails" are designed to solve the problem. They are designed to be shaped like a nail, are long enough to insert into the end of a standard caulk tube nozzle, and will extend past the nozzle length down into the tube area.
I would also suggest printing the nail in the color of the caulk for quick identification.