that is sort of what I do.
I buy 2 liter and one gallon jugs... though.. two liters and long neck bottle water bottles work best. If you are covering a large area a gallon jug is your best bet.
But, for deep rooting in a pot take your bottle screw the lid on tight and cut the very end off. ( Not the end with the lid) You want to remove less then 1/4 inch all together because this is the collection spot.
Take a safety pin and just below the lid, prick a hole in the plastic. 2 holes work best, but one hole is just as efficient.
Bury the neck of the bottle along the edge of the pot with the hole facing the bottom of your plant. The deeper you do it, the deeper the roots have to grow to reach water.
With the end that you cut off facing up, all you have to do to water your plants is to pour water into the bottle and it will drop in your plants roots for a long time.
In long droughts, or high heat, this saves your plants from being burned.
It also conserves water as it gives the plants just what it needs, right where it needs it with out having to drench the entire pot in water.
When it rains, it will collect the water too.
For gallon jugs, or super large pots ( Like trees) again with the safety pin, but this time put your holes on the bottom of the jug and cut off the very top where the lid is. One gallon should water for an entire day.
Refill your jugs every other day or every 3 days st the most.
You can ad your fertilizer right to your water as well and use only 1/2 the recommended dosage because it goes directly to the roots.