On a weekend trip dealing with dirty laundry is not too much of a concern, but anything longer than that and the socks and underwear will start piling up. What are you supposed to do with all that on the go?
One option is to bring along a plastic bag to toss stuff into, but many people don’t use plastic bags all too much anymore. A good alternative is getting a travel laundry bag such as the one from Miamica.
The key is to find something that will keep the laundry separate from the rest of your clothing. This is both to avoid re wearing something dirty and also so that it doesn’t stink up the rest of your bag. A good laundry bag will zip open and closed with ease, hold a decent amount of clothes, and ideally will be labeled so that you always grab the correct bag.