I try where I can to use pop bottles with pin holes in the caps and around the tops with the bottoms cut off to turned upside down and buried in the ground to assist me in watering at depth, so the root system of the plants goes and looks for the water rather than surface watering which is especially important for root vegetables.
2 Litre pop bottles are better as one can pop the hose head into the pop bottle, the small 330ml coke bottles fit neatly into smaller weed membrane planting sheets but they don't have the capacity for holding the hose head.
Long slender necked 1 litre Tonic Water bottles are idea as they give you the best of both worlds, a nice long slender neck and a diameter that will allow the hose head in.
But as I don't use to many tonic water bottles I've made the best of both worlds by cutting a hole in the top of a 2 litre bottle just big enough to pull a 300ml pop bottle through and create a seal.
Necessity is the mother of invention