Sinbad youth hostel is a good example of "you get what you pay for." The rooms are dense with bunkbeds and the top bunks are not too stable. The bathrooms aren't super clean, and can get crowded.
However, the staff are super friendly and helpful. There is a terrace upstairs where breakfast is served, and presumably you could hang out there also, but it doesn't seem like anyone does. All the extras at the hostel, such as food at the restaurant and internet access, are more expensive than elsewhere in Istanbul. Unfortunately, they don't allow you to bring your own food out onto the terrace to eat, and there isn't anywhere else where you can self-cater.
One nice plus about this place is that it isn't located near the dense area of all the other hostels. It's on a relatively quiet street and there are no clubs nearby, so you won't be kept awake by the bars. There are some great restaurants on that street, and it's the sort of area where things are normally priced instead of inflated tourist prices.
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-- Exclusive Hostelz.com Review