I'm not sure there's a definitive 'most popular' list for Sprunki stories on Wattpad that holds up across the board. The algorithm there tends to favor stories that update frequently and get a lot of early traction through comments and votes, which doesn't always mean they're the best-written. From what I've seen scrolling through the tag, a lot of the top-ranked ones follow a very similar pattern: human reader or OC gets thrown into the Pizzaplex, meets the Glamrocks, and there's an immediate protective dynamic with Freddy. They can be fun, sure, but after a while they all start to blend together for me.
What I find more interesting are the slightly off-center takes that have dedicated followings. There's one where the protagonist is a night guard who's actually competent and slowly pieces together the lore, treating the animatronics with a mix of caution and respect instead of instant familiarity. The romance, if you can call it that, builds over dozens of chapters. It's not in the top ten, but the comments section is full of people deeply invested in the mystery. Another one that comes to mind is a crossover fusion with 'The Magnus Archives', where the Pizzaplex is a domain of one of the fears. It's niche as hell, but the people who are into it are into it. The popular stuff is easy to find, but the real gems require some digging past the first few pages of results.