I think I know how it could work.
Someone gives both a truth AND dare:
Truth: “Have you ever thrown up at school?”
Dare: “Change into a bathing suit right here, with the lights on without using a towel.”
Next person picks one.
Truth…answer it regular. “Yes, but a long time ago” or “I’m sure I have, but I don’t remember.”
Dare… If you were in a room with your friends, would you do it? (You could answer something like “of course!” or “only if it was all girls because I don’t want guys to see me change into a bathing suit.”)