CHRISTOPHER: What about last night? What did our having sex mean to you?
LORELAI: [sighs] It meant that Jose Cuervo still has amazing magical powers.
Jose Cuervo is a Mexican brand of tequila. It is the best-selling tequila in the world, and has a third of the American market.
Lorelai is making it clear to Christopher that she would never have had sex with him if she hadn’t been drunk. By saying that it “still has magical powers”, she also implies that was the case when they were teenagers.