Bring a medium pot of water to a boil. Add the carrots and cook until crisp-tender, about 1 minute. Drain and rinse under cold water until cool. Pack the carrots and dill sprigs into a 1-quart jar.
Make the brine: Combine the vinegar, 3/4 cup water, the sugar, 2 1/2 teaspoons salt, the dill seeds, caraway seeds and 1/4 teaspoon pepper in a medium saucepan and bring to a boil.
Pour the hot brine into the jar and let cool completely. Cover and refrigerate overnight or up to 1 week.