We visited the test kitchen where Sonic develops bizarre creations like pickle slushes. Here’s what it’s like.

• Fast-food chains like Sonic spend months inventing and testing craveable creations before they hit the menu.
• We visited Sonic’s test kitchen inside its headquarters in Oklahoma City to get an inside look at how the hot dogs get made.
• Sonic’s chef, Scott Uehlein, fed us new and upcoming menu items, from a pickle juice slush to a Philly cheesesteak on a hot-dog bun with Baja sauce.

The idea of putting pickle juice in a slushie seems like a fever dream of a brine-obsessed mad scientist. However, for Scott Uehlein, it’s just another day of work.

Uehlein is Sonic’s vice president of product innovation and development. He spends his days conceptualizing, creating, and testing new creations that might one day find a spot on the menu at the fast-food chain – like the pickle juice slush, which hit menus in June.

On a recent trip to Oklahoma City, we had a chance to stop by Sonic’s headquarters. And, while we were there, we dined on a full – perhaps overstuffed – menu of new and upcoming creations from the fast-food chain’s test kitchen:

Sonic's test kitchen is inside the company's headquarters in Oklahoma City, mere feet away from an actual Sonic location that's open to the public.

However, Uehlein and his culinary team don't need to venture outside of the headquarters to try the fast-food chain's menu items.

Sonic's new culinary innovation center has a full kitchen where items are created and tested. Ovens, grills, and other gear are on wheels, so they can be rearranged to mimic various kitchen set-ups, ensuring it is actually feasible to speedily prepare new menu items.

Uehlein served us a spread of new and upcoming items that he and his team had created in the test kitchen. Sonic executives are often presented with a rundown of new and potential dishes at the culinary center. We got the executive treatment: a full menu and spit cups.

We started out with the pickle juice slush. It's a baffling beverage — the pickle flavor is clear and present, which should be an immediate turn-off. And yet, we kept finding ourselves taking another sip. It's sweet, but not saccharine. Somehow, it works. Life is baffling.

Part of the power of the pickle juice slush was Uehlein's clever pairing. Uehlein paired the pickle juice slush with the crispy chicken tenders, which debuted in June.

The new tenders are a shift from the super-crunchy trend that took over fast food in the '90s. Now, a Chick-fil-A-obsessed America wants a less carb-y, less battered option. The tenders are a solid iteration of the genre. More importantly, the salty strips pair perfectly with the sour pickle juice slush.

After the success of the pretzel twist in January, Sonic decided to craft a sweet version of the menu item. It's fantastic — the pretzel base's sweet-and-salty mix, when dunked with cream-cheese frosting, begs to be devoured.

One of Uehlein's most ambitious projects has been the part-mushroom, part-beef Slinger. Created as part of the James Beard Foundation's initiative to encourage "blended" burgers made with mushrooms to promote sustainability, the Slinger was the first burger of its kind to hit fast-food menus.

The burger doesn't sacrifice taste for its sustainable and low-cal brags. The patty itself is nice, with the mushroom adding some subtle nutty tones, but the real star is the sweet and soft brioche bun, a weapon more fast-food chains should add to their arsenal.

The bun also features in Sonic's breakfast sandwich, which will hit menus when the Slinger returns in September. A chain with a menu as extensive as Sonic needs to find versatility for ingredients — and this is a great way to do it.

As breakfast sandwich fanatics, we think Sonic's is an extremely worthy addition to the field. Closest in flavor to Shake Shack's breakfast sandwiches, this Sonic uses a few simple ingredients — eggs, cheese, buttery brioche — to craft a delectable sandwich.

Perhaps the most controversial menu item we had a chance to try outside of the pickle slush was Sonic's take on the Philly Cheesesteak ... on a hot dog bun. It's a dish only Sonic could create, using ingredients already on the menu — beef, hot dog buns, even Baja cheese sauce.

Following in the grand tradition of fast-food-snack icon crossovers (see: Taco Bell's Doritos Locos tacos, Burger King's short-lived Mac N Cheetos), Sonic is teaming up with Oreo for a new, late summer ice cream cone.

The menu item doesn't simply use the Oreo cookie as the cone. Instead, the inside of the cone is coated with the unmistakable sweet cream that binds the Oreo together, a a saccharine goop that quickly hardens with contact to the cold ice cream. It's a decadent, double-stuff-inspired treat we highly recommend.

We got a glimpse at a few other menu items in the pipeline at Sonic that we can't show because they're still in the testing stages. They might appear on menus drastically differently months down the road, or they may never show up at all. Making the perfect fast-food menu item takes time — but Scott Uehlein is the man for the job.