The first time I passed out, I went unconscious and hit the wall; fortunately there were people around to help/wake me up.
The third/fourth attempts I got horribly nauseous and had to sit down instantly, not being able to get up for at least 5-10 minutes while drinking juice/something with sugar.
I make sure I get up slowly and carefully, but the moment I do, I have at most 5-10 seconds to sit down before I pass-out again.
I'm trying a Water Fast again; I'm only on day one and feel fine, but I'm nervous to see what day 3 is like.