We highly recommed to book an accomodation as soon as possible – June is high season in Interlaken.

Interlaken has a wide range of hotels in different categories. 

Here are a few recommendations for group accomodations (besides Airbnb):

Homepage

Prices start at CHF 48.00  pP (group accomodation for 6 persons, shared toilet/shower on hallway) up to CHF 61.00 pP (4 persons, shower/toilet in the room)

Included:
breakfast (all you can eat)
sheets (all beds made up) and a towel
private lockers in all rooms
use of self catering kitchen: 24 hours
high speed WiFi in the whole building and all rooms
free entry to public in- and outdoor swimming pools
free Minigolf and Tennis
free use of public busses
parking
all taxes

Homepage

(For young people who enjoy the nightlife)

Alpenblick (right at the lake of Thun) offers group accomodation in tents: Homepage

Manor Farm (right at the lake of Thun): Hompage