I've been reading about how the INDY 500 bottle of Milk tradition started and I've seen a handful of different accounts. Louis Meyer either in 1933 or 1936 is sited most often... and it is usually regular milk, but sometimes it is Buttermilk. Seems like Dario Resta had a bottle of milk after the 1916 Vanderbilt Cup race in Santa Monica (no photo of that though).

Go to WhereTheyRaced.com for more racing history, a few vintage INDY cars, lots of ghost tracks and automotive innovation.