Amsterdam also offers a lot of amazing hotels and hostels located in and around the city centre, see for example hotels.com and booking.com. You could also rent via Airbnb, and spend a night on a houseboat or in a canal house, for instance. If you are travelling to Amsterdam on a shoestring, your cheapest option is to Couchsurf during your stay.
Sonic Acts deal Stayokay Vondelpark
Especially for Sonic Acts visitors, the Stayokay Vondelpark offers a discount of 2,50 per night on online booking for the 26th till the 29th of February 2016. Get the discount by using the promo code SONIC16 during booking
Situated in the middle of Amsterdam’s most famous park, Stayokay Vondelpark is within walking distance of most of the festival locations. The hostel has 2-, 4- and 6-bedded rooms and some large dormitories. Each room has its own private shower and toilet. You will be given bed linen upon arrival to make your own bed. Towels are not included. There is free wifi in the lobby. Check-in is from 14:00h on, check-out is at 10:30h. Address: Zandpad 5, 1054 GA Amsterdam.
Check out their website
for more information.