I used to work for an old eccentric lady who grew oleanders like crazy. She was always on the lookout for that unique oleander flower and would raise cuttings. I think she had a bad memory, because every few days she would tell me about how easy it would be to kill someone by putting some ground up leaf in lemonade. Then one day after a hard day at work in the summer sun, she offered me some lemonade. GULP! I tried to act as if I wasn't thirsty, but she kept insisting. I caved and drank it. WHEW! I quit that job soon after that day. Too weird and scary for me.

I wouldn't try to get water from a poisonous plant unless I had no other option.