Make cake: Preheat oven to 350°. Grease a 9"-x-13" baking pan with cooking spray and line with parchment paper.
In a large mixing bowl, whisk together cake mix, oil, and eggs until smooth and combined. Slowly whisk in Coke until fully combined. Pour batter into prepared pan.
Bake until a toothpick inserted into the middle comes out clean, 25 minutes. Let cool completely, then cut cake into 1" cubes.
Meanwhile, make frosting: In a large mixing bowl using a hand mixer, beat cream cheese, butter, and sugar until light and fluffy. Add in cream, rum, vanilla, and salt and beat until medium-stiff peaks form.
Place 4 cake cubes in the bottom of each serving glass, top with a dollop of rum whipped cream, and drizzle with caramel. Repeat layering until glasses are full.
Serve with a rum nip toppled upside-down in each glass.
Recipe by 5* trending recipes with videos at https://food.theffeed.com/2022/01/25/rum-coke-cakes/