We feel that wine is wine through our sense perception/organs of senses: taste, colour, smell, touch, the dizziness it creates (I guess, I have numbered all of them, or almost all of them). Now, there is not a logical impossibility that there is no actual wine and God incites our sense perception organs so, that we feel 100% that we are drinking wine and getting dizzy, and all those feelings are 100% the same and this inebriation influences our health in absolutely the same way if we had drunk an actual wine. Then there will be no difference whatsoever in drinking actual wine and in having an absolutely same perception while God giving us an impression of drinking wine. In fact, even drinking actual wine produces in us an impression and influences our health, and if God-given impression (albeit without actual wine) produces the same impression and influences our health in the same way, there is no difference whatsoever, and it will be absolutely impossible for us to take ourselves out of our skins and see the difference, for we do not have any supra-senses/transcendent-senses to observe our senses as it were from outside, but all we get are senses we get.
However, God cannot do this to us, as Descartes has proven very well in his 4th meditation, because, He is not a deceiver, and if we have such a strong inclination to believe that the outer world influencing our senses exist, then (given that God is not a deceiver and it is He who gave us our senses), this world really exists out there. Taken into a consideration this general principle and taking into consideration that Jesus being God cannot deceive, then He did not influence sensual organs of people directly, without real presence of real wine, but truly gave them wine, which He miraculously produced out of water.
Having established that, we can hazard whatever pious interpretation of why did He use water and what symbolic-metaphoric-educational significance did He put there. I will provide just one such interpretation, for an example and a template, but far better and more spiritual and paradoxical interpretations, of course, are infinitely possible:
six jars were destined not for wine but for water used in ritual of cleansing (John 2:6), and Jesus shows by the miracle that the maximum degree of cleansing available in Jewish tradition before Him was not enough to infect humans with divine grace and make them crazy, make them inebriated by the divine madness of New Commandment "be perfect as your Heavenly Father is perfect" (Matthew 5:48) in order to "love each other as I have loved you" (John 15:12). The cleansing by water signified a possibility of leading a virtuous life within human terms and capacities, the wine into which this water turned, thus, signified inadequacy and insufficiency of this virtuous life with reference to divine life, which seems a crazed type of life for all, who don't accept Christ as God and Saviour and are not led by Holy Spirit (cf. 1 Cor. 1:18; 2:14).