public class Sender extends AsyncTask<String, String, String> {

    private static final OkHttpClient client = new OkHttpClient();

        protected String doInBackground(String... params) {

            try {

                //FormBody.Builder formParam= new FormBody.Builder();
                //formParam.add("access_token", "токен");
                //formParam.add("v", "5.73");
                //formParam.add("user_ids", "1");
                //RequestBody formBody = formParam.build();

                JSONObject obj = new JSONObject();
                obj.put("access_token", "токен");
                obj.put("v", "5.73");
                obj.put("user_ids", "1");
                RequestBody jsonBody = RequestBody.create(MediaType.parse("application/json; charset=utf-8"),
                        obj.toString());



                Request request = new Request.Builder()

                        .url("https://api.vk.com/method/"+params[0])
                        .post(jsonBody )
                        .build();

                Response response = client.newCall(request).execute();


                return response.body().string();

            } catch (Exception e) {

                e.printStackTrace();
            }

            return "fail";

        }
}

Sender handler = new Sender();

result = handler.execute("users.get").get();