Student or Learner
Is it OK to say "You need to do your homework for the next day"?
Is it better to say"....for the following day"?
Is there a reason you don't want to say "tomorrow"?
Perhaps you mean something repeated. Each day when you get home, the first thing you must do is your homework for the next day.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.