A peek is a very quick glance at something. To peek (verb) is to look quickly. In this way, this spelling makes perfect sense for the term “sneak peek,” as it is often a very short look at the upcoming product or offering. A peak, on the other hand, usually refers to the highest point of something. This most commonly comes with the imagery ... More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.