How do you hold your pee for a long time?!

One of you is going to give. There's only so much the bladder can hold, and there's only so much strength your urethral sphincter can muster to keep the pee from bursting out. Who knows, maybe your bladder has a lower capacity than your girlfriend's, so you'll end up bursting first.

If you don't want to have an "accident" while in public, you might want to think of backing off on the idea.

If you're a guy, you can sort-of cheat by tying your member tight... which of course can be potentially harmful to your said member. There are some common medications (which I'm not going to mention) that can cause urinary retention, but you often get other more harmful effects first before the urinary retention thing. Therefore, also not recommended.

Pardon that momentary tone of sarcasm. Bottom line is, you're body's going to find a way to extrude your waste (unless there's a stone or solid obstruction blocking your urethra, which in that case you have to see a doctor quick before you damage your kidneys as well).

Peace out!

you idiots!
its very unhealthy to hold in your pee, and the way i see it the both of you are going to spend hours of not going to the bathroom just to beat the other moron.

so stop the bet and bet on who can suck on the others genitalia and making them *** the fastest.
this way both of you have fun out of it.
dont bet on thing that are gonna be a pain in the ***, bet on something thats gonna be fun!

Holding your urine depends on the size of your bladder and if you have exercised it in the past by holding off as long as you can.

Really not a recommended thing to do; can stretch or even tear the bladder, causing scarring and loss of urine pressure. Bet something that isn't stupid.

Don't think about it and when you can't stop thinking about it hold on to it real tight and that will buy you some time.

Dont drink anything. Dont piss.