Mix cornmeal, cream-style corn, clams, onion, flour, baking powder, salt, and sugar in a bowl until batter is thoroughly combined. If batter is too thick, stir in milk, about 1 tablespoon at a time.
Heat oil in a deep-fryer or large saucepan to 350 degrees F (175 degrees C).
Scoop about 1 heaping tablespoon of batter per fritter and gently drop into the hot oil; deep-fry in small batches of 3 or 4 fritters until golden brown, 3 to 4 minutes. Drain fritters on paper towels.