I want a moderate-hard challenge, I can only drink water and I want mine to involve public/hidden public

Drink 1L of water per hour for 3 hours, then hold for 2 more. Do 50 exercises of your choice, and if you fail, stay in those clothes until you go to bed.

Drink 2L of water in 2 hours and hold for 1 more. If you fail, you can't go to the bathroom for the rest of the day.

Drink 1 glass of ice tea every 10 minutes for an hour. Hold for 1 hour after. If you fail, only drink iced tea for the rest of the day.

Drink 500 mL of water and 500 mL of coffee each hour for 3 hours. Hold until you really have to go, then drive to the nearest public bathroom and go there.

Drink 500 mL of water every 30 minutes for 2 hours. Wait two hours, then drive or walk to the nearest public restroom.

I would like to have the hard one...moreover in a dirty manner

This puppy would like a medium to hard challenge. Preferably not involving workouts.

Drinking pee and extending the time maybe for failure, other punishments you prefer are also fine instead or in combination.

Something hidden public, or covert public in the process (for either drinking the failure, or what you want to come up with).

I have available: Water, Tea, Coco (can't drink pure milk), Beer (can safely drink two bottles within two hours), Coffee

I do live in a village though have a train ride into a larger town ahead of me tomorrow. The ride takes about one hour each direction, and I have shopping business in town for about an hour as well.
The train usually has a lockable toilet space. There are public toilets at the city train station.

I would love a medium to hard dare involving diapers. I have water, milk, and tea to drink.

Drink 3L of water in 3 hours, and hold for 2 more hours. You can only go in a public restroom.

Drink 2L of water in 2 hours. Bring an extra liter bottle for the train into the town. Drink it along the way. Then you must walk to the nearest business, and you can go there.

Drink 500 mL of milk and 500 mL of water each hour for 2 hours. Hold for 2 more hours.

How hard do you want it? Extreme
What do you have to drink? Water, Milk (Warm or Cold)
Do you want any other rules? Extra time for failure, Keira can pick the rest

Hold for 8 hours, drink 4L of water within the first 5. If you fail, you must try it again, only for 9 hours.

How hard do you want it? Moderate

What do you have to drink? Water, Juice, soda

Do you want any other rules? Can throw in some edging & humiliation if you want. Maybe a nice “reward” if I complete the dare & punishment if I fail. I’ve got some embarrassing undies and a few pullups that could be used as punishment, Keira can decide what she thinks is appropriate