I'm travelling to the Netherlands and I'm visiting 4 cities in the span of 8 days, so it's going to be quick. I'm travelling with just a hand luggage and I haven't considered booking an hotel, that would be my last option. I thought about couchsurfing but it seems that nobody wants to host someone who recently created an account. What other ways do I have to get a place to rest and take a shower? I'm intending to be in Eindhoven, Rotterdam, The Hague and Amsterdam (maybe not in that order)
With the distances involved (short) and the time spend on traveling from hotel to hotel, I would chose a central location and 'commute' from there. Rotterdam, the Hague and Amsterdam are within an hour from each other, with the Hague just south of the middle point.
I would spend a night or two in Eindhoven (if you want that) and see the city as well as do a bike ride in the countryside or do a bus travel in the local area, by local bus is likely the best option.
Then travel to the Hague, (use a booking site to get a hotel there,) and stay for the rest of your trip. Take a train to Rotterdam one or two days or use the metro line for at least one of your travels, take a train to Amsterdam, for one or two days, two routes to keep looking out of the window interesting.
You could stay in any of the three cities, the Hague has the edge because it is mostly in the middle, but it also has a 'beach area' which will have cheaper options out of the summer season and business hotels which will be cheaper when there is little business travel.
One of the options would be to find a place by Airbnb in a city which is relatively close to your destinations (Leiden or The Hague).
But you should calculate it carefully. You will save on the accommodation costs but will add in transportations costs.
Eindhoven still stays furthest from these places, but it is relatively small city and doesn't require much time to explore. I would rather visit Utrecht, Leiden or Haarlem. But it depends on the goal of your visit and your interests.
There are other sites like couchsurfing, but I think they operate the same way. You are not expected to ask for a couch as a substitute of a Hostel.
If you want to keep trying couchsurfing, you will more likely find a host if you:
Have fixed schedule. People have more guests coming, work, etc. If you know the exact dates they can be more/less sure that they can host you
If you ask a week in advance (at least) for the same reasons.
If you send direct requests to specific persons / you show interest on what they do or can teach you or you know something they show interested in (languages, travel experience, ethnic cooking abilities...). Just read they profile and write a thoughtful request.
Having said that I hope you find a host and start embracing and enyoing the CS way of traveling.