What of these is the most performant way to iterate through a loop?

Which of the three approaches below is the best? Probably a dumb question but I'm always questioning myself. I could imagine that once you do more than one action with an item in a loop it would be better to cache it first but at the same time you're making a new variable each time you go through a list which makes me doubt it. Any insight on the best approach? Thanks! //This one: Note that I'm not storing a list item in a new variable for(int i = 0; i