Show the white milk. Explain that God is perfect but we are not. We have all sinned. Read Romans 3:23 and add some black food coloring to the milk to make it dark or murky. Read Romans 5:8. Explain that God sent Jesus to be the Savior of the world. Even though we have all sinned, God showed His love for us. Read Romans 6:23. Jesus made a way for us to have eternal life but you have to be willing to receive Christ as your Lord and Savior…Pour the liquid into a paper cone. And once your accept Christ into your life and ask Him to forgive your sin…Open the cone to show no liquid. Jesus makes your sins disappear.
As a second idea, you could also talk about how some people go through the motions of “pouring” Jesus into their lives but He’s not really there. They look good on the outside but are missing Christ on the inside.