For watering my plants, I found that laundry detergent bottles work fantastic. My wife had some 2 gallon Tide detergents that she finished with and I gave them a really good cleanup (although it's mostly just a surfactant and most plants actually like surfactants because it helps them draw water, so clean it good, but no need to be paranoid).
The great thing is that they have a push button spout, so you can just hold the lip over your plant and push the button. I'm doing hempy buckets, so I'm having to mix up hydro nutes, and I have to mix up a new batch of nutes about every 2-3 days with my plants. They are much more durable than milk jugs and much handier