Whisk 1/2 cup plain Greek yogurt, 1/2 cup mayonnaise, 2 tablespoons water, 2 tablespoons apple cider vinegar, 2 minced garlic cloves, 1/2 teaspoon kosher salt, and 1/4 teaspoon freshly ground black pepper together in a large bowl until emulsified and well-combined; set aside.
Arrange a rack in the middle of the oven and heat the oven to 400°F. Line a rimmed baking sheet with aluminum foil. Arrange 1 pound of bacon in a single layer on the baking sheet. Bake until the bacon is deep golden-brown and crisp, 15 to 20 minutes. Meanwhile, bring a large pot of salted water to a boil.
Add 1 pound dried short pasta to the boiling water and cook according to package directions until al dente. Drain and rinse with cold water to cool. Drain well. Transfer the bacon to a paper towel-lined plate. Once cool, crumble the bacon into bite-sized pieces.
Add the drained pasta, bacon, 1 pint halved cherry tomatoes, 3 ounces coarsely chopped spinach, and 3 tablespoons finely chopped chives to the dressing. Toss to coat. Cover and refrigerate for at least 30 minutes before serving.
