Cook bacon in a large nonstick skillet over medium heat until crisp, 5 to 6 mintues. Drain on paper towels, then crumble bacon. Pour off all but 2 teaspoons drippings.
Add tomatoes and onions to skillet and stir-fry 2 to 3 minutes until tomato skins just start to split and onions are crisp-tender. Transfer to a large serving bowl and add the spinach.
Add chicken to skillet and cook 7 to 8 minutes, turning once, until golden brown and opaque at center. Remove to a cutting board.
Add dressing and water to skillet, bring to a simmer and remove from heat.
Cut chicken crosswise in 3/4" wide slices; add to bowl. Add hot dressing and bacon. Toss to mix and coat.
Per serving: 239 cal, 10g fat, 28 g pro, 411 mg sod, 67 mg chol.