First, stake your plastic sheeting down on all 4 corners (you can cut the sheet in half so teams are separated)
Squirt the soap out over the plastic sheeting
Spray water all over the plastic sheeting and the soap to get it sudsy and slippery
place 2 buckets on one end of the slide - near the corners
place 2 more on the other end - near the corners
Fill 2 of the buckets that are on the same side with water
Place a cup in each filled water bucket and have kids line up behind it into 2 even teams
When you're ready, kids should scoop a cup of water out of the filled water bucket and run as fast as they can to the empty bucket to fill it
They want to run fast, but if they fall - they risk spilling their water and they won't have any to fill the empty bucket with