Make the batter. Combine cornstarch, all-purpose flour and baking soda in a bowl. Make a well in the center, then stir in 1/4 cup of cold water to make a smooth batter. Add salt, pepper and minced shallot.
Coat the shrimp and vegetables with batter. Toss the shrimp, bean sprouts and sweet potato strips into the batter and give the mixture a good stir until everything is coated.
Cook the fritters. In a large non-stick frying pan over medium-high heat, add vegetable oil just enough to cover the pan as want to cook the fritters in just a touch of oil. Spoon out a heap of the mixture with a tablespoon into the pan to form fritters. Cook in batches for 3 minutes on each side, or until golden, firm and cooked through. Repeat with the remaining mixture, adding more oil to the pan, if needed. Drain on a paper towel.
Make the dipping sauce. Stir together vinegar, garlic, salt and pepper in a small bowl, then serve with the fritters.