Using an empty beverage bottle with a twist top, a drip button and a punch tool, you can make cheap irrigation bottles for potted or hanging plants. Similar set ups cost about $10 retail, so aside from recycling, you're saving money too! I had drip buttons left over from a previous project, but new they are less than a dollar. The tool was about $2.
Step 1: Enjoy A Beverage
Finish off a tasty beverage with a twist top. Cut off the label.
Step 2: Punch A Hole In Top
Using a fair amount of force, push the punch tool through the top. This is what the hole should look like.
Step 3: Insert Button
This takes a good amount if force, as the button is meant for much thinner plastic.
Step 4: Add Water And Invert!
This is a 17oz bottle with a 1/4 gph drip. You can fill it with water, make a small hole in the soil and let gravity to the rest. You can use large bottles, like a milk jug or a large juice bottle. These could also be suspended from above. A cheap way to bring water to your plants and reuse a container. The drip is much slower than I expected due to the vacuum effect. You could make a pin hole in the top for ventilation and a more consistent flow.