Elton John couldn't hold it while shopping for sneakers over in France, and ended up pissing in a plastic bottle in the middle of a store ... so says the guy who runs the shop.

Ryan Sukkar, owner of Sugarkikz in Nice, tells TMZ ... Elton came into his shop Monday afternoon with his 2 sons and a bodyguard and asked if there was a public restroom.

When Elton was told there wasn't a toilet around, the shop owner says the singer turned to his security and asked for a bottle ... then took a few steps away from other shoppers and began taking a leak in the receptacle.

Sounds like Elton's got poor aim ... we're told he got some pee on the floor and asked his security for a towel to clean up the mess.

The shop owner says he was "shocked and frustrated" a customer would take a tinkle like that ... and this was a first in his 3 years running the business.

Seems Elton really had Ryan's head spinning ... he says he had no idea who EJ was when this was all going down, and when he asked Elton what he did for a living, the singer simply responded, "I'm Elton John." Classic Elton, really.

Ryan says he did a quick search online, and that's when he realized this was a huge deal. In the end, we're told Elton bought 2 pairs of sneakers for his sons, snapped a picture for the store and shook hands with Ryan before leaving.

No word if he used his "pee hand" during the salutation, but there was no mention of the pee-pee incident.

And Ryan clearly wasn't crying over spilled urine, because he tells us ... overall, Elton was very cool.

When you're Elton John, the world is your toilet!!!