In Order of Phoenix, Ch. 38, The Second War Begins, they read "Sunday Prophet".
Harry was sitting on the end of Ron's bed and they were both listening to Hermione read the front page of the Sunday Prophet.
Wikia says that it's an edition of Daily Prophet, like Evening Prophet is.
But their only proof - very weak one IMHO - is that there is a Daily Prophet example published on Sunday - specifically, 4/13/2014 - Ginny Weasley Quidditch report "Norway vs Ivory Coast". However, that link doesn't actually say "Sunday Prophet" anywhere on it!
Is there an actual solid canon proof that Sunday Prophet is an edition of The Daily Prophet aside from this "not called Sunday Prophet" example and a mere fact that they are both called "Prophet" (which is evidence, but there's 1000s of Muggle newspapers called "News" or "Post" so it's not exactly proof).
Notably, Pottermore's Daily Prophet article mentions Evening Prophet but NOT Sunday.