Slightly off-topic: In the past, when I've donated blood, they often had donuts and juice for donors after the donation process was over. granted, if someone normally eats healthy, one snack of (mostly) junk food won't harm them. I don't know if this post-donation snack was meant to prevent someone from feeling faint, as I've heard happens to some donors; I've never had a problem.
Lol, i donated blood only once (for my ex-husband's father). And i fainted after that! It happened on our way to their home, right in a suburban train, and we nearly missed our stop.
But(!) i wasn't vegan then... so 1) before getting on the train, my MIL persuaded me to devour a stinky meat pie ("khyicheen")! ...plus 2) before donating blood, nurses had made me drink disgusting super-sweet tea, which i loathe, and eat a decent piece of roasted bread ("sukhar' "). No wonder, i felt nauseated all the time, and my stomach was very upset, and when i feel nausea, i already have a semi-unconscious condition, so it's easy to faint, especially when you've just have given away 450 ml of blood.
Well, at least the "process" of blood donation was interesting. My dad had been trying to talk me out of doing it, but i had been determined, so i wasn't afraid, because i knew, that without the blood of 3 of us (hubby, MIL and me), he would have died. Unfortunately, he died anyway.