This root was one of a surprisingly large number of roots Tolkien used for “juice”, appearing unglossed in The Etymologies of the 1930s with derivatives like ᴹQ. pirya/peich “juice, syrup” and N. pichen “juicy” (Ety/PIS). A similar primitive form ᴱ✶pisye appeared in Early Noldorin Word-lists from the 1920s, with derivatives ᴱQ. pihye/ᴱN. hí “sap, juice” (PE13/147). This in turn might have been a later iteration of unglossed root ᴱ√PḶQḶ from the Qenya Lexicon of the 1910s with a single derivative: ᴱQ. pulqe “juice”.
Neo-Eldarin: For purposes of Neo-Eldarin, I would assume this root refers mainly to syrup and tree sap, as opposed to fruit juice which would be derived from ᴹ√SAB.
An unglossed root in the Qenya Lexicon of the 1910s with derivatives ᴱQ. mark “ripe juice, sap, ooze, moisture” and ᴱQ. marqa “oozy, juicy, moist” (QL/63); Tolkien marked the root with a “?”. There are no signs of this root in Tolkien’s later writing.