What likely happened is they sounded to dilate their urethra, then pumped cum lube up their urethra while still a bit soft / not flexing their kegel muscles so that their ejaculatory duct (the tube where cum shoots out of) would stay closed but their external urethra duct (the tube that connects to the bladder and then merges with the ejaculatory duct to form the urethra) would be open and it went up into their bladder. Then, they kept it there by getting hard / flexing their kegels to shut the external urethra duct and open the ejaculatory duct and held the cumlube in their bladder. Then they used the pump to get as big and hard as possible, and while using it filmed themselves repeatedly flexing and unflexing their kegels to piss out cum lube in little spurts. It’s the exact same muscle rhythm that the body does to shoot out cum upon ejaculation, except ironically this person is doing it backwards, firing cum out from the bladder rather than the ejac duct. Very sneaky, sis…

Also yes given that cum lube isn’t exactly guaranteed to be sterile, and the urethra is obviously built to be a one-way street so going that deep and sending liquids deeper in liable to go wrong / go up into the ejac duct / cause some damage this is a risky practice. Not the worst thing in the world tbh, like if all precautions are made then one can probably get away with doing this without any long-lasting problems, but yeah this is the fast lane to getting a UTI. Not very fun.