If I am a full-time student and I'm being sued by a bank, what are my options?

I assume you are being sued by the bank because you owe them money, probably an unpaid debt such as a credit card balance.  If so, it matters little that you are a fulltime student.  You still owe the money.  Your best option probably is to negotiate with the bank or the bank's attorney to settle the matter.  Your alternative is to lose the lawsuit and have a judgment entered against you that will haunt you until you pay it off.