Why do we drink wine on Shabbat when it's stated in the Kiddush (כִּי הוּא יוֹם תְּחִלָּה) that this is a day of tequila?
It's because of the double gezeiras-shav. Yom Kippur is referred to as Shabbos Shabason, and Yom Kippur itself is only ki-purim. So the halakhic wine from Purim is transferred to Shabbos. But since ein mikra yotzei midei peshuto, tequila is still a recommended drink between courses (or anytime one's spouse goes into the kitchen to get something). But it is also a Binyan Av so any hard alcohol or mixed drink suffices for this purpose.