Florida residents on a late-night taco run were treated to a chimichanga special ... but not the mouth-watering kind.

Here's the deal ... the Flagler County Sheriff’s Office says it received a call very early Thursday morning from Taco Bell employees reporting what the sheriff's office has jokingly said was a man with his "chimichanga" out, according to local outlet WFTV.

The office says authorities arrived and allegedly discovered Brandon Irizarry -- a 28-year-old man -- outside the restaurant with multiple pairs of pants pulled down.

Irizarry was taken into custody ... which is when officers say they discovered a live betta fish swimming inside a container in his backpack.

The betta fish has been named "Baja Blast" by deputies and was handed over to the Flagler County Humane Society for care. The fish is reportedly doing well.

Sheriff Rick Staly said in a statement, "In Flagler County, if you can’t keep your business inside your pants, you’ll find yourself at the Green Roof Inn, swimming with different company than your fish."

Cops booked Irizarry on an unlawful exposure of sexual organs charge. His bond was set at $5K.

Taco Bell encourages customers to "Live Más" ... but they should remember to wear más clothes, too!