If Jesus calls himself "the true bread" or bread of life (antitype), what is the type? The natural or ordinary bread. If Jesus is the "true vine", what is the type? The natural vine itself. If Jesus is the ideal or good Shephard, then the type is Shephard itself. Spiritual truths are implied from physical, natural objects.
Charles Ellicott writes,
(1) I am the true vine.—For the word “true,” comp. Note on Joh. 1:9. The ideal truth, of which the natural vine is a figure, is fulfilled in Him. The thought is introduced suddenly, and with nothing in the context to lead up to it. The natural explanation of this is, that here, as in other instances, it was suggested by some external object which met the eye. If we suppose (comp. Note on Joh. 14:31) that they were crossing the valley on the way to Gethsemane, there is reason for the idea that they passed a vineyard, that supplied the form in which our Lord’s thoughts are expressed; but the journey itself, during the discourse, is improbable; and the sight of a vineyard is the less likely, as it was night. On the supposition that they were still in the room where they had eaten supper, a vine whose tendrils grew into the room, or the vine carved on the doors of the Temple (Jos. Wars, v. 5, § 4; Ant. xv. 11, § 3), or the vineyards seen in the distance by moonlight, or the vine suggested by “the fruit of the vine” of which they had drunk, have been suggested. Of these the last has most probability, as bound up with the significance of the cup of which they had drunk that night. We cannot say more than this. The imagery may have followed from some incident, or custom, or remark, now wholly unknown to us. It was, as in the case of the Good Shepherd, familiar to them from the Old Testament, and would have come to their minds from any slight suggestion. (See, e.g., the following passages: Psa. 80:8-19; Isa. 5:1 et seq.; Jer. 2:21; Eze. 19:10.) It seems to have been expressed also in Rabbinic precepts, e.g., “Whosoever dreameth of a vine-branch shall see the Messiah.” (Berachoth, fol. 89.) And my Father is the husbandman.—Comp. Mat. 21:33 et seq.; Mar. 12:1 et seq.; Luk. 20:9 et seq. The thought here is of the owner of the vine, who himself cultivates and trains it.
John Gill comments:
whether he might take occasion, from the sight of a real vine, to compare himself to one, nay be considered; since it was usual with Christ, upon sight or mention of natural things, to take the opportunity of treating of spiritual ones: though it may be rather this discourse of the vine and branches might be occasioned by his speaking of the fruit of the vine, at the time he ate the passover, and instituted the ordinance of the supper.
Jesus' blood is the true wine, that was symbolized by the natural red wine during the Passover Seder. To quote from my answer from this question- Why did the disciples not protest on the statement of drinking the blood of Jesus?:
Red wine as the symbol of the blood of the first Passover lamb
The Jews were already familiar with the symbolism of the blood in red wine, in the Passover Seder. See the book Jesus in the Passover: More than an Haggadah by Ton Rose, or the basic articles or videos describing the meaning of the Seder, by Mark Biltz. The wine is also called the blood of grapes. The red wine in the Seder represents the blood of the lamb, and some sages interpreted it as the blood of the children that the Pharaoh murdered. The cup institution is a secondary extension to the Seder plate, it is also interpreted mystically, read the meaning of the four cups in detail in Kitzur Shulchan Arukh 118:1.
Shabbat 129a:14 מַאי צׇרְכֵי סְעוּדָה? רַב אָמַר: בָּשָׂר, וּשְׁמוּאֵל אָמַר: יַיִן. רַב אָמַר: בָּשָׂר — נַפְשָׁא חֲלַף נַפְשָׁא. וּשְׁמוּאֵל אָמַר: יַיִן — סוּמָּקָא חֲלַף סוּמָּקָא. The Gemara asks: What are these special needs of a meal? Rav said: It is referring to meat. And Shmuel said: It is referring to wine. The Gemara explains: Rav says: It is referring to meat because the soul replaces the soul, i.e., the meat replenishes the person’s strength. And Shmuel said: It is referring to wine because the red replaces the red, i.e., red wine substitutes for red blood.
To quote Dov from Judaism SE, on the blood symbolism of the red wine:
The starting point is the Shulchan Aruch OC 472:11 where it writes expressly:
מצוה לחזור אחר יין אדום (אם אין הלבן משובח ממנו) (טור):
It's a mitzvah to seek red wine (if the white wine is not better) [Tur].
The Kitzur Shulchan Aruch 118:1 writes further the reason why:
You should do your best to obtain choice wine to perform the mitzvah of drinking the Four Cups. If red wine is available, that is, of the same quality as white wine, and its kashrus is as reliable as white wine, the red wine is preferred for the Four Cups, for it is said, "Look not after wine when it is red," (Proverbs 23:31) indicating that wine is most desirable, when it is red. In addition, because it reminds us of the blood, which flowed, when Pharaoh slaughtered innocent Jewish children. In backward and ignorant countries, where people, make slanderous accusations, Jews refrain from using red wine on Pesach. (Sefaria translation)
This point about the slaughtered children is also mentioned in the Ohr Zaruah, Vol. II, Siman 256 (Left column, bottom quarter) and he adds two other symbolic cases of blood. He writes:
יין אדום זכר לדבר שהיה פרעה שוחט תינוקות כשנצטרע ועוד זכר לדם פסח ולדם מילה
Red wine as a remembrance for Pharoah who slaughtered the babies (and bathed in their blood) when he was suffering with leprosy. And furthermore, it is a remembrance for the blood of the Korban Pesach (the Paschal Lamb) and the blood of milah (circumcision).
Finally, it is also worth noting the Pri Megadim, OC, Eishel Avraham 472:13 who writes that when using wine it should be red as it resembles blood and is a remembrance of the first plague of blood, thus symbolically appropriate for the evening, in the same way that Charoses is a remembrance to the cement/clay that the Jews used.