Gaining that much weight within such a short time is generally quite unhealthy. You can do serious damage to your body by doing so. Perhaps you should speak with a doctor before you decide to do it. On the other hand, carbohydrates and red meat proteins can pack a lot of weight in a short time.
increase your daily meals up to 6 times in a day instead of taking heavy meal three times.. in every hour just eat something.. it could be any fruit or dry fruit. go for healthy food instead of junk food. in the morning after work out don't forget to drink one big cup of banana shake.. banana really works..