Every fall, the Arizona Fall League takes places as a short offseason league that allows some (but most certainly not all) of the game’s top prospects to get some extra work in. There are specific rules for how many players from each organization can play and from which levels of the minors, etc. plus there are often some “interesting” inclusions based on roster needs in the AFL.
The Braves have had some really exciting players play in the AFL in recent years including most recently Ronald Acuna Jr. and Austin Riley who really showed out down there.