How can I build a Rube Goldberg machine with 20 steps?

I'm so stressed. My friend and I are trying to build a Rube Goldberg machine with 20 steps and 3 simple machines. It's really hard. Maybe we are using the wrong idea and/or approaching it a bad way. So far, we have the ending. We're trying to water a plant. We have a liter bottle and it's hanging in midair by string and a hanger. We also have a tube on the nozzle also hung up by string and a hanger. We were going to pop a water balloon inside the bottle but it's so hard to figure out how to pop it. Should we just try another idea or approach it a different way? What's something easy we can do? We only have 3 days left to finish it.