Other forms: sneak peeks
A sneak peek is a chance to see something that hasn't been released to the public yet. There's nothing like being let in on a secret to make you feel special.
Often, a sneak peek is for products that are going to be released or sold, but aren't out yet. A celebrity chef might offer a sneak peek of her new sauces to food reporters (hopefully with a tasting). At a comic convention, you might see a sneak peek of a superhero film that comes out next month. But you can also use it more generally: "I just took a sneak peek at that diary; I didn't read the whole thing!"