Place onions and carrots in a medium-sized bowl and set aside. Pour the vinegar into a small bowl. Add the sugar and salt and stir until the sugar dissolves. Pour the vinegar solution over the onions and carrots and transfer the bowl to the fridge. Let sit overnight.
For the Salsa
Place all ingredients in a medium-sized bowl and stir to combine. Transfer the bowl to the fridge and let chill for at least 1 hour before serving.
For the Tacos
In a large mixing bowl, whisk the flour, baking soda, cumin, salt and cayenne pepper together. Add the corn, garlic and the jalapeño to the dry ingredients and toss to coat. Pour in the beer and stir until a thick batter forms. Set aside.
In a large heavy bottom pot, heat the canola oil over medium-high heat until it reaches 350°F. Using an ice cream scoop, scoop the batter into the hot oil, 5-6 scoops at a time. Fry the fritters until golden brown, about 5-7 minutes. Transfer the fritters to a plate lined with paper towel to dry.
Place two fritters in a corn or flour tortilla and top with radish salsa, pickled carrots, a dollop of yogurt and sprinkling of fresh cilantro. Repeat until all the tortillas are filled.
Serve the tacos immediately with a lot of cold beer