Combine the shallots, garlic, oregano, sugar, olive oil, vinegar, lime juice, tequila, salt, and pepper in a gallon-sized sealable bag; shake to combine. Add the tilapia to the mixture and store in the refrigerator 2 to 4 hours, turning every 30 minutes.
Preheat oven to 450 degrees F (230 degrees C). Line a baking sheet with aluminum foil and prepare the surface with cooking spray.
Arrange the fish on the prepared baking sheet. Discard remaining marinade.
Bake in the preheated oven until the fish flakes easily with a fork, about 10 minutes.