Combine okra, onion, green tomato, jalapeno pepper, and garlic in a large bowl. Whisk milk, eggs, salt, and black pepper together in a separate bowl; pour over vegetables and toss to coat. Gradually add cornmeal to vegetable mixture until liquid is absorbed and ingredients are moist and evenly mixed.
Heat oil in a skillet over medium heat; spoon batter into skillet. Reduce heat to medium-low and cover. Fry until bottom of fritter is browned, 10 to 15 minutes. Flip fritter and fry until other side is browned, 5 to 8 minutes. Cut into slices to serve.