Nothing more than a bit of warm water, shake vigorously for a minute or so, stick in a bottle brush that I have bent to shape, swirl that around a few times, empty and warm water rinse and shake again. I'll then put a very diluted mixture of an oxy product and leave it in there for a while. When I come to use it, a starsan or similar. It does say that you can also stick them in an over at 80 degrees to sanitise but i've not done that.
My mate has built an outdoor jig for his that holds 6 at a time and he jet washes the inside of his on a lower pressure jet. Works well.