In a microwave-safe bowl or in a pan on the stovetop combine vinegar, water, sugar, and salt. Heat for 2-3 minutes until mixture is hot. Remove from microwave or stove and stir until sugar has dissolved.
Place carrots in a medium heat-proof bowl, pour hot vinegar mixture over carrot. Add fish sauce and gently stir. Cover with a paper towel, gently pressing into the carrots until it absorbs the liquid, this allows for the carrots to be covered with the quick pickle liquid. Let cool. Store in refrigerator in a tightly sealed container for up to two weeks. Drain before use.
In a medium bowl, combine all mayonnaise ingredients. Stir well to combine. Refrigerate until ready to assemble sandwiches.
To Make the Sandwiches:
Cook sliced sausages on the stovetop or grill until heated through. While sausage is cooking, remove some of the inside of the bread to ensure your sandwich is not too doughy. Lightly toast in the oven or on the grill.
Assemble the Sandwich:
Divide the seasoned mayonnaise between the four rolls, place two slices of sausage (one whole sausage) on the bottom piece, top the sausage with a few sprigs of cilantro, mint leaves, jalapenos and about a ¼ cup of pickled carrots. Secure the sandwich with the top of the baguette or bun. Serve immediately.