There actually is a kind of sake made with saliva, Kuchikamizake. It was invented before Japan had other forms of fermentation, so they would chew the rice to kick-start the process.
Oh? This sake is delicious!Glug GlugIt's sake that Reimu made!♪It came out especially good this time!♪Glug GlugGonna brewwww it!♡Hm-hm...that silly girl, that's about all she has going for her.Come to think of it, isn't shrine maiden sake made from saliva?