Is the question seeking those who happened to not eat animal by-products? Or for moral reasons didn't eat animal by-products. I wouldn't call someone avoiding non-kosher a vegan.

Also Moshe ate no animal products while on Mt Sinai.

@robev I was thinking more towards the second reason, but this is fine.

@AA Moshe is different as he neither ate nor drank anything while he was on Sinai. That is a totally different situation

@sabba why is that different than this case? Both are people who didn't eat meat temporarily under certain circumstances.

@AA Is a vegan someone who doesn’t eat animal products, or one who only eats plant products?

@DonielF That is a tough חקירה to work with ;-).

@DonielF I don't know, but either way Moshe qualified. Maybe close the question for now since clearly it's pretty unclear what exactly is being sought?

@AA Being a vegan means restrictions on your menu, while being in fast means you have no menu at all. I agree that Hanania, Mishael an Azaria were not vegans due to the reasons that usually cause people to turn vegans, but it's close.

@AA As far as I know a Vegan is someone who does not eat meat as a matter of principle. Thus, Doniel and Moshe would not have been Vegans as they ate meat when they could. Calling them Vegans would be like calling someone who was unable to get to the butcher shop a Vegan.