This article is a travel topic
The longer you travel, the more likely you'll need to wash your clothes. You can:
Note that if you are charged by the kilo and the clothing is already wet, you'll pay a whole lot more. Allow the items to dry out first, or negotiate a lower rate.
The cheapest way to do your laundry (albeit not the most thorough) is to do it yourself. If staying at a hotel, make sure this is not against the rules.