I leave the pop bottle whole. Punch holes in base. This way I fill bottle and put lid back on. This way it takes the water longer to come out of bottle and you don't lose water too fast or drown you plants. NOTE: do not punch holes too big. Works for indoor plants too, just choose a smaller bottle. I fill bottle right at plant so I don't have to fight with a leaky bottle.
You can cut the bottom off the bottle and drill small holes into the cap. Put the neck area in the region of the roots, and it will self-water once you fill with water in the open end.
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