In a large bowl, mix flour and chile. Whisk in soda water until a pancake batter consistency is achieved. Completely coat the crab in the batter. Lightly drop in 350 degree F oil and fry for 4 to 5 minutes until golden brown. Season with salt and drain on paper towels.
In a non-reactive saucepan, heat the vinegar, chile, salt and sugar until just boiling. Add the cabbage, carrots and garlic and simmer for only 3 minutes. Pull off the stove and let cool. Transfer to a glass container with an air tight lid. Store in refrigerator overnight. Will keep for 3 to 4 weeks as long as you do not introduce bacteria to it, ie. your finger.
Plating: Place a small mound of slaw on the bottom piece of bread. Top with 1 crab and top with a little more slaw. Cover with top piece of bread and slice in half.