What's a commonly forgotten item that I can be a bro for bringing?

Going out for my first track day and tagging along with a fun group of folks who are more experienced. How can I do them all a solid? via /r/Trackdays https://www.reddit.com/r/Trackdays/comments/bk3mjj/whats_a_commonly_forgotten_item_that_i_can_be_a/?utm_source=ifttt