I have no idea what hold ups are, but the thing that is important to how you wash a thing is what the material is. In general, oxygenating whiteners like OxyClean are a safer way to whiten things than chlorine bleach, so unless the material is something that this is known to be a bad idea for, I would try a soak in that.

You can try a bleach dilution on an older pair. Something you might otherwise throw away. Start with 5:1 water to bleach and try stronger concentrations until you get the desired results. Make sure you measure and record your measurements so you know the ratio that works best

Disclaimer: This could ruin your clothes. You should see what others have to say before trying. I'm a scientist not a... person who knows useful things

Hold ups?

Is that a Bra?

Not a lady and have no hold ups, but if you want your whites to maintain that crispy, clean brightness, you should try Mrs. Stewart's Liquid Bluing. That shit's magic.

I just toss mine in the wash but I also do not give a damn so like... 🤷🙃 Also, to be fair, have never been a fan of them myself and can't say I've worn them more than like a handful of times in my life.