You can water from cans. You really ought to be saving as much as you can into butts. I have several around the garden off sheds and the greenhouse and will be tapping into the bungalow roof guttering next. Also let the cover on the picnic table form pockets which collect water then drain these off into buckets.
Water saving tips also include regular hoeing in between plants so any dampness, dew etc get soak down to the roots and use plenty of mulch such as compost, old leaves or even gravel or bark chippings.