Let's make a bet - and the looser has to do ...
What about this one:
There are 2 girls that are around 18 to 20. They always compete against each other and make strange bets (I think you can compare it to jackass)
Or they make some kind of bet. It could be about something like the superbowl or another sports event. And here comes the Lit-Part. The looser oft he bet has to do something naughty, something erotic.
It could be like: who will win the Superbowl? The girl who looses has to run around nude on the street for an entire minute. Regarding the fact that they are living in a quiet suburban area, this is not so risky ...
The loosing girl takes off her clothes and covers herself with a coat. Then she leaves the house and walks around naked for an entire minute ... but she wants to get even ...
A few days later, they go to a public mixed sauna. Usually, everyone is nude in there. (this ain't fantasy. In Europe (at least in Germany) this is normal in a sauna).
It can be like: they argue who of them can hold their breath longer. They both dive under the water surface and the one who gets up first looses.
Or: usually (as far as I know) in many saunas, there is a small pool with very cold water, to cool down after the hot sauna cabin. As far as I know, this water is around 55°F (about 13° C) or less. Which one of them can stay longer in the cold water [Usually, I stay in there for a few short moments - I think 60 seconds maximum - but I once talked to a woman who was sitting in the cool pool for like 15 minutes ...]
This time, flashing ain't enough, since everyone is nude in the sauna. It could be like: lay naked on a recliner, with your legs spread wide open for a minute or 2. Being nude amongst other nudes is one thing, but with spread wide legs, giving everyone a good view on the pussy is naughtier.
While she is laying there, with her legs spread wide, the loosing girl has enough time to think about some new punishment for the other girl - and this time, it should involve a stranger. Maybe they should offer a stranger to touch the boobs of the loser girl. Or maybe even the pussy? Or even hotter - the loser girl could offer a strange guy a handjob or even a blowjob ...
"We have done so much, with so little, for so long, that now we can do almost anything with nothing." - Dave Marcis