What language is this from? Is it a variant of Mandarin or another Chinese language?

My reasons for confusion 头水：my Pinyin keyboard doesn’t even want to write this. Is this supposed to be 口水？

小豆脑：is this some metaphor?

‘My saliva is gone. I want that those electrolytes give me tofu brain [very soft tofu for other people reading], very constipated’

I’m a very confused Chinese learner.

Edit before responding: I think I understand the metaphor now lol