Is this an idiom, a mistranslation, a reference to a cultural practice, or something else entirely?
The Codex Vaticanus text for this passage is:
The Latin also says 'wine':
The NETS translators note at least three major Greek versions of the book of Tobit, the second (GII) is reflected in the text above. Be sure to read their introduction to the book for more information.
Codex Sinaiticus omits verses 7b-18, and the Aramaic has not been preserved. Some have posited that Tobit 4:3b-19 is an interpolation,2 while others believe its absence in Sinaiticus is likely accidental.3
But the practice referenced in this text appears to come from another contemporary text (and may have been cited verbatim):
Interestingly, Tobit 1:22 mentions someone by the name of Αχιαχαρος (Achiacharos), which can be transliterated as Ahiqar:
It should be noted that this follows the first Greek version noted by the NETS translators (GI), while the second (GII) also says that Ahiqar served under Sennachereim, king of the Assyrians, and then was appointed second by Sacherdonos.
The text says that Tobit's nephew is an official in the court of Esar-haddon at Ninevah, and this may be the same Ahiqar who composed the proverbs that were the source of v. 17 (or perhaps merely to whom they are attributed, cf. The Story of Ahiqar).
Jonas Greenfield (cited in the Eerdman's quote above) is the most notable scholar to note the relationship between Tobit and the Proverbs/Wisdom of Ahiqar. He presented this idea to the American Oriental Society in 1967, but I have been unable to find the actual article, which is fully cited in footnote #5 for your reference (and if you find it, please share!).5
1 The Vulgate numbers this as verse 18 of chapter 4.
2cf. Paul Deselaers. Das Buch Tobit (Univ.-Verlag; Göttingen: Vandenhoeck & Ruprecht, 1982), 50, 380-92. Also Merten Rabenau. Studien zum Buch Tobit (Berlin: Walter de Gruyter, 1994), 51-65, 149-50.
3 cf. Francis M. Macatangay. The Wisdom Instructions in the Book of Tobit (Berlin: Walter de Gruyter, 2011), 45ff, especially section 2.1.3.
4 James D.G. Dunn & John W. Rogerson. Eerdmans Commentary on the Bible (Cambridge, UK: Wm. B. Eerdmans Publishing Co., 2003), 741.
5 J.C. Greenfield. "Ahiqar in the Book of Tobit," in De la Torah au Messie: Melanges: Etudes d'exegese et d'hermeneutique bibliques offertes a Henri Gazelle (ed. J. Dore, P. Grelot, and M. Carrez; Paris, 1981), 329-36.