Syncing styles can be enabled per layer. To do this, toggle the Sync Text Layer Styles option on the ContentSync Layer Inspector. Then each style property can be toggled to sync.
Enabling syncing text style properties.
When enabled, ContentSync will try to map styles between the spreadsheet and the text field. Each spreadsheet does have limited styling abilities so read more about each spreadsheet's support for more details.
For example, Google Spreadsheets does not support decimal font sizes.