In a 9 x13 pan, bake cake according to directions. Cool and crumble. Make pudding according to package directions, with milk.
In a large trifle or other glass serving bowl, place half of the crumbled cake. Pour half of the coffee over the cake, and spread half of the pudding over that. Top with half of the whipped topping, sprinkled with half of the crushed candy bars. Repeat layers in the same order. Refrigerate until serving.
Wendy's notes: When I made this I decided to leave out the coffee and it tasted fine. I also used a large package of pudding mix.