Can I use iPhone as a burner phone?

Our nonprofit organization is worried over the power US border guards have over digital devices and we want to avoid the awkward situation of us refusing to provide account information. We're an all Mac environment with staff using iPhones.

I'd like us to have a 'burner iPhone'. Basically a cheap/old iPhone that staff can pop their SIM card into, and then they travel with this iPhone into USA. The iPhone would not have any apps or contain any files. When staff arrive in USA, they can then download the apps they needed (e.g. Twitter, Google Drive, etc...).

Is this possible?

Or would the 'burner iPhone' for some reason automatically start syncing with the staff person's iPhone the moment the SIM card is popped in? (e.g. downloading apps, files, etc...)

Thanks!