Preheat the oven to 400 degrees. Spray a 9 x 13-inch baking sheet with nonstick cooking spray. Cut the chicken breasts into ½ inch strips. In a large bowl mix together the mayonnaise and the milk. Place Doritos and the taco seasoning in a ziplock baggie, crush the chips into medium-sized crumbs. Pour the chip mixture into a medium-size bowl.
Coat the chicken strips in the mayonnaise mixture and then roll in the crushed Doritos mixture. Place onto a baking sheet in a single layer (be sure not to overlap).
Place into the oven and bake at 400 degrees for 10-12 minutes or until the chicken is fully cooked (the internal temperature has reached 165 degrees).