That's something you'd have to build from the ground up, while using the original code's functions for other similar systems as references. Personally, I'd just duplicate the core functions related to the system of breast milk/fluid stored in the body via creampies and then refer to the system regarding "orifices" when dealing with the mouth.
I'm not entirely sure what you're specifically wanting to do, so I'll assume you're trying to implement something akin to breast milk where the character stored and regenerates quantifiable amounts of saliva. In that case, yes, you'd have to essentially learn how Innoxia has setup the system and figure out which files are the core components of the functionality. I'd look at "character/FluidStored.java," "character/body/[FluidInterface.java, FluidMilk.java, and AbstractFluidtype.java]," all the files with "Fluid" in the name in "character/body/valueEnums," and make liberal use of the functions in "character/GameCharacter.java."