In a bowl, mix sugar, salt, and 3/4 tsp. anise seeds. Add shrimp and stir gently to coat. Cover and chill 45 minutes to 1 hour. Rinse both the shrimp and the bowl well and drain.
Meanwhile, soak 6 wooden skewers at least 30 minutes, or use metal skewers (no need to soak).
Return shrimp to bowl. Add remaining 3/4 tsp. anise seeds, the olive oil, 2 tbsp. ouzo, and the garlic; mix to coat. Thread shrimp onto skewers through each end so they look like the letter C, dividing them equally among skewers.
Prepare a charcoal or gas grill for high heat (450° to 550°; you can hold your hand 5 in. above cooking grate only 2 to 4 seconds).
Lay shrimp on cooking grate and cook, turning once, until shrimp are bright pink and opaque but still moist-looking in center (cut to test), 2 to 3 minutes total. Transfer to a platter. Drizzle more ouzo over shrimp if you like.
Note: Nutritional analysis is per serving.