Your question is somewhat vague, but I have generally found that sincerity goes a long way. A heartfelt statement at sentencing, and an acknowledgment of wrongdoing will usually mean something to a judge. Character reference letters can also help. On the other hand, if the judge or the prosecutor believe that the defendant is trying to "play"them, that will usually blow up any hope for a lenient sentence. Best advice, ask your fiance's lawyer what can be done. Good luck.
The response I have provided is general in nature, and does not create an attorney-client relationship. My practice is based in Rhode Island, and the law and practice in other states or jurisdictions may be different.
Are you asking about how he should present himself to the Judge for sentencing? If so, given that his attorney knows his case better than any of us ever could, I believe he should be asking this of his attorney.
If he is free on bond before sentencing he needs to get a job, get treatment, pay child support if he has children, pay his bills and stay out of trouble. Show up at sentencing without a job and without treatment the judge will think he isn't a productive member of society anyway, why not send him to prison to dry out and keep him from being a thief or at least a leach on his family, girlfriend or someone else. Everyone in jail finds Jesus and promises this is the last time.....Watch some sentencings.