Add onion and garlic. Cook over medium to medium-high heat, stirring often, until onions begin to soften, about 5 minutes. Add taco seasoning; cook and stir until fragrant, 1 to 2 minutes. Stir in black beans, corn, and diced tomatoes. Stir in tomato juice and scrape any browned bits of food off the bottom of the pan with a wooden spoon.