A good routine if you don’t have any equipment is to do some push-ups (you can do different types of push ups), do some push ups (also do different types), and some squats. If you manage to make a 100 of each that should get you in moderate shape IMO, maybe if you have fat in a specific part of the body and you want to get rid of that you should do some specific exercise in that area, but I think that’s a workout plan that does not require that much time. Also don’t try to do 100 push ups one after the other, you should try and do 10, then 20, and so on, and doing everything slowly is better than doing it fast.