"Fifteen years later, I'm still in search of a sandwich that tastes just like that. So this morning, I decided to get up and try to create a sandwich just like that for the summer," she said.
However, fans have pointed out there's a Schlotzsky's restaurant that seems to have two locations in Las Vegas, where Spears had a long-term concert residency.
"She's gonna be p***ed when she finds out she could've had Schlotzsky's delivered all these years during captivity" one fan commented on her Instagram.
This then led to many of her fans question why the singer never visited those locations while living there.
But that wasn't the only thing fans were confused about.
Spears lays out the ingredients for her sandwich which includes ciabatta bread, avocado, lettuce and shredded chicken and turkey.
The singer then mentions how the sandwich's unlikely combination of goat cheese and almonds creates "very, very good flavour".
But fans could not get over how she was cutting almonds that actually looked a lot like pecans, and Spears ended up correcting herself in the caption, writing "PS I meant pecans not almonds !!!!"
"Nothing looks more dangerous than Britney Spears cutting pecans" one fan commented.
"Queen of cutting almonds with one hand" another fan commented.
While showing more ingredients, Spears zoomed in on some "sheared pears" that oddly resembled fish.
"It looks like fish but it's not; it's very sweet and it adds a really different taste to the sandwich," she adds.
Spears showed off the final product and cut herself a tiny piece of the sandwich to enjoy.
"A little goes a long way; you don't need a huge sandwich for the summertime. Something kind of small and a little French will do it for me," she says. "And voila! It's a beautiful little sandwich."