Well, we're not a space station to recycle our urine, yet it's possible to have a portable desalinating machine onboard (or just use condensation process it some extreme situations).
Plastic waste possible to transform in a fuel or repairing material for the boats (for this you'll need more space, tho)
And if you got an old cargo ship you cat have not only a breadfruit plant , but many others, but we don't have one yet:)