I dry fast regularly (no water, no food). At about day 6 my dreams are so lucid and vivid that I can basically control them if I wake up in the middle of the night (and when you dry fast, waking up and being pretty much alert is common around days 3+ of a dry fast, at least for me). It's pretty crazy and one of the things I look forward to the most each time I dry fast (about 5 times a year, 7 days or so each time).