Fill a cocktail shaker with ice, then add pineapple juice, tequila, fresh lime juice, and Cointreau. Secure lid, then shake for 10-12 seconds to aerate the drink.
This step is optional, but adds so much flavor and is delicious for snacking! Heat a large grill pan or grill over medium-high heat. When hot, grill pineapple wedges until just charred. Set aside.
Run a lime wedge along the rim of the glass. Strain into glasses, then add 1-2 jalapeño slices to each drink. Garnish with grilled pineapple wedges.