I have created a fun and tasty science experiment for students. I think this would be a great emergency kit to have in your car, just incase the sub plans are a little light or there aren't any at all! All you need is a bag of gummi worms, a pack of cups and this sheet. You can get both the worms amd the cups at a Dollar Store. So for only $2-$3 you can have a good back up that will keep the kids interested for a good amount of time at the beginning and the end of the day.
The Incredible Gummi Worm
I have a few other fun things at TeachersPayTeachers.com.