Preheat oven to 350°F. Spray silicone cupcake pans with nonstick spray.
Prepare yellow cake mix per box directions. Fill 12 jumbo cups. Bake, cool, then remove.
Prepare brownie mix per box directions. Pour into a greased 9x13 pan. Bake and let cool completely. Cut into circles using a 2.5-inch cutter.
Divide frosting into two bowls. Tint one red for "ketchup" and one yellow for "mustard."
Place shredded coconut in a bag, add green food coloring, and shake to create "lettuce."
Slice each cupcake in half horizontally.
Assemble: Pipe yellow frosting on bottom half, add strawberry slices and a thin layer of white frosting.
Place brownie patty on top. Pipe red frosting around edge, top with green coconut.
Add top cupcake half. Brush with corn syrup mixed with water, then sprinkle with sesame seeds.