Making a sub choose between being able to cum and being able to empty their bladder is the hottest thing.
Make them edge every day for a week (or longer), so they're a desperate, needy mess by play day.
Then lock the bathroom before they wake up on play day. Keep that bladder nice and full on play day. Keep plying them with drinks, so it keeps getting fuller, until the evening when they're bursting and begging.
Once they start begging to pee, have them lay naked on the bed, and spend an hour or two teasing and edging them, until both of their needs are at their peak.
That's when you give them their choice.. piss, or cum. Only one.
But here's the part that doesn't get talked about enough:
Consequences of their decision.
Ok, so you chose to piss. Probably a good idea since you look like you're about to wet yourself any second. But you're going to spend the next 24 hours being teased and edged, with only enough breaks to eat, sleep, and piss in between. You might get to cum tomorrow night. Or you might have to just wait until we play again next weekend...
OR
Ok, so you chose to cum. I can see why, you're so needy you can't even form a coherent sentence. But I hope you didn't think you were going to get to cum and then just hold it for an hour or two until you wet yourself and let that be the end of it. No. From now until bedtime tomorrow night, you're holding. If I decide it looks like you really can't hold it anymore, I'll let you piss for 5 seconds. Just enough to keep the dam from breaking. Then you'll cut it off, pull your pants back up, and we're going back out. Yes, we're going to be in public. Did you think I would just let you stay home so you can have as many "accidents" as you want?
If you *DO* have an accident, I'm just going to have you drink enough to fill right back up. So don't even think about it.
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Let each consequence be enough torture that they want to choose the other next time, every time.
