Hi there Juanema I have used plastic bottles ( usually green) and put a small hole in the bottom and the top to drip into some of my pots. I can keep them hydrated but becareful as your sun will be a lot hotter than mine and it can also reflect the heat.
I have used larger laundry soap containers in the yard to water a new plant for a longer time with a drip. I just use a toothpick in the out spout and partialy undu the screw top to allow the water to escape out the toothpick jammed open spout at the bottom. You can play a little bit to get the flow or drip you need. If you don't release the top cap you end up with a vacume and no water will escape into the soil.
Hope this helps.