Throw them all in the wash and go commando, maybe throw a panty liner in there. Define dirty underwear? If they've got discharge or something on them then probably not. If they don't look/smell gross, and I just know I've worn them already, then I might. (What? I'm human.) Hand wash really quickly, dry them (blowdryer?) Bathing suit bottoms?
I would instantly wash a pair and tumble dry them.
I never wear jeans to begin with. Just dresses or yoga pants lol. I also have like 400 pairs of panties so not having any clean ones really isn't an option but for the sake of answering the question, I would just not wear any, I hate them anyway.
That hasn't happened to me, since I have plenty of underwear and wash them regularly. If that happened though, I guess I'd hand wash a pair in the sink, quickly dry them and wear that. Never wear dirty underwear. It's too hot right now for commando, and I hate chaffing.