Vietnamese Style Grilled Shrimp Sandwiches

1 garlic clove, thinly sliced
3 tsp. sugar
3 tbsp. water
1 tsp. kosher salt
4 tbsp. fish sauce
2 tbsp. lime juice
2 seedless cucumbers, thinly sliced
2 tbsp. rice wine vinegar
1 tsp. salt
1 tsp. sugar
8 small French rolls
2 lb. peeled shrimp, grilled
3 carrots, shredded
Bean sprouts, as needed
2 cups mixed herbs (basil, mint, cilantro, and rau raum, if available)
Pickled jalapeños, for garnish