Hello and welcome to Apple Support Communities le_danielle,
We see that you have a question about signing up for two premium Fitbit accounts with one Apple ID. We'd be happy to provide you with some information that can help.
You would only be able to have one subscription under one Apple ID. You could create an Apple ID for your husband if he does not currently have one. If he already has an Apple ID, then you could just use the Apple ID that he has. If he does not have an Apple ID of his own currently, and you're concerned about him losing access to other apps, music or other purchases that have been made under your Apple ID, you can set up Family Sharing.
We have included the links below to create a new Apple ID and how to set up Family Sharing.
How to create a new Apple ID
Set up Family Sharing
If you have additional questions regarding the Fitbit premium, take a look at the support link below.
fitbit
Thank you for using Apple Support Communities.