Here's my advice, which is probably why too late for most of you.
Save underwear that you're ready to throw away and pack it for vacation. Then, wear it and throw it away. No suitcase full of dirty underwear when you get home! You can do the same with other clothes, depending on the type of vacation.
Hey, don't knock nasty underwear! I credit my dirty underwear for why, when I was 18 and flying back with my sister, separate from my parents, as the reason they didn't open my bags which had the bottle of scotch I legally in Scotland bought for my dad that they made me carry because they already bought their duty free limit . Certainly not legal for my 18 year old self to bring in (what were my parents thinking?!)
Another packing cube tip, I bring an extra large cube for dirty laundry. It prevents mixing with clean, and if I'm on a longer trip, it's a very easy container for laundry during the trip.
In many countries it's pretty customary and inexpensive to just drop at a laundromat or the front desk of a hotel, same day service. This allows you to pack lighter, too. Or you can take a couple hours off and do it yourself, but it's often not that much cheaper.
Of course this is entirely dependent on where you're traveling. But so many places I've traveled to do not have home washers, including my current situation, and certainly no dryers (try balcony doing during rainy season without direct sun!), so it's pretty culturally common to utilize a service.
At minimum, bring those multi purpose washing and dryer sheets so you don't have have to purchase if you choose to do your own, although my laundromat automatically includes the suds. Or bring powder to wash in a sink.