There are products called sounds that are made for this, but other objects, including fingers will work as the urethra is stretched to accommodate them.
Urethral sounding involves inserting a toy into the urethra — the tube that drains urine out of the bladder.
It is therefore much better to stretch your urethra first and only attempt penetration later.
And there is 193 more Urethral Sounding free videos.
You may also want to try a smaller or thinner toy.
And women are especially prone to urinary tract infection, so do not be careless.
This and activity that carries certain risks but this should not scare you.
Try Sex in the Urethra If you want to try to have sex in the urethra, it is important to be relaxed.