NSHTTPCookieStorage *storage = [NSHTTPCookieStorage sharedHTTPCookieStorage];
for (NSHTTPCookie *cookie in [storage cookies]) {
    [storage deleteCookie:cookie];
}

NSHTTPCookieStorage* cookies = [NSHTTPCookieStorage sharedHTTPCookieStorage];

NSArray *facebookCookies =
    [cookies cookiesForURL:[NSURL URLWithString:@"http://m.facebook.com"]];

for (NSHTTPCookie *cookie in facebookCookies) {
    [cookies deleteCookie:cookie];
}