Yes, you can deduct maintenance fees for your timeshare rental (prorate the amount if you used the timeshare personally).
Here's how to do this in TurboTax Online:
There isn't a drop down to add an expense. What do I do now?
If you're using TurboTax Online, to go the rental property summary page and click "Add Expense or Asset." Miscellaneous expenses should appear at the bottom of the next page.
If you're using TurboTax Desktop, click Start/Update beside "Expenses" on the rental summary screen. "Any miscellaneous expenses?" appears after several other questions.