When I saw these in a teacher magazine, I knew I wanted it, but the price tag just turned me away every year. I tried the plastic baggy from the window, but found they don't grow very big. And as I learned you do not put tape on the windows, or you'll be scrapping the windows to get the sticky stuff off. If you could find another way to attach them to the window, maybe 3M hooks would work, they are great to see the roots of the plant. But, I want to produce vegetables.
Take the wrapper off. Cut the top off the bottle. Make sure it is clean. Left over sugar will effect the growth of your plants. (Interesting science experiment for later)
Put dirt in the empty bottle. Add seeds as close to the edge of the bottle as possible. Make sure you water it well. Watch the seeds sprout. Plants grow up and roots grow down.