Corrected entry: During the strip poker game, Kari says, "I'll bet you my thongs." Thongs are what flip-flops were called in the 80's but she was wearing tennis shoes the whole scene, you have to bet with the clothing you are wearing in strip poker.
An American Summer (1990)
1 corrected entry
Directed by: James Slocum
Starring: Brian Austin Green, Michael Landes, Joanna Kerns
Continuity mistake: Tom and Finn bury a rope in the sand after tying it to the lifeguard stand but the next day they pull up a chain instead.
Kari: I'll bet you my thongs.
Finn: OK, I'll bet you my underwear and raise you a truth or dare.
Kari: What? You can't bet a truth or dare!
Finn: Just because I ran out of clothes doesn't mean I can't still bet.
Correction: Thong is a type of underwear. That's what she was referring to.
Bishop73
This correction is wrong. I remember this movie, so I found and watched it on YouTube and the girl definitely says "thongs", plural, so I'm inclined to agree with the original post that she was indeed referring to sandals and not underwear.