Put your juice in a container that has room to add more liquid and is deep enough that you can submerge an egg. Gently place the egg in the container. At this point it will probably sink straight to the bottom, so don’t just drop it in. If it heads to the bottom, remove it and add about 1/2 cup of the simple syrup. Stir and try the egg again.
This time when you put the egg in it should be suspended in the liquid, maybe not to the surface yet, but hovering just below. Refer to the step-by-step photos above where I am pointing at the faint white spot under the surface. Remove the egg.
Add another 1/2 cup of the simple syrup and stir.
Place the egg in the sorbet, now you can see it starting to emerge. It needs to be about the size of a quarter above the surface to indicate that there is enough sugar in your solution.
Add simple syrup a couple of tablespoons at a time until you have the right level.
Once it is floating high enough, add the liquor or liqueur of your choosing.
Pour into your ice cream maker and proceed according to the manufacturer’s instructions. Tip: I freeze a container to the put the sorbet in so it won’t melt when I remove it from the machine.