1Heat oven to 350°F (325°F for dark or nonstick pan). Grease and flour or spray bottom and sides of 13x9-inch pan.
2In large bowl, beat cake mix, water, oil, vanilla and eggs with electric mixer on low speed 30 seconds, then on medium speed 2 minutes, scraping bowl occasionally. Pour into pan.
3Bake as directed on box for 13x9-inch pan. Let stand 5 minutes. Poke top of hot cake every 1/2 inch with long-tined fork, wiping fork occasionally to reduce sticking.
4In large bowl, stir together sweetened condensed milk, whole milk and whipping cream. Carefully pour evenly over top of cake. Cover; refrigerate about 1 hour or until mixture is absorbed into cake. Frost with frosting. Store covered in refrigerator.