You can have several Google accounts simultaneously in your mobile device. Many applications allow you to open different Google accounts straight from the application. Ie. in Gmail application you can change the account by tapping the top bar and choosing the correct account. Some applications, like Google+, demand you to log out from the application to log in with other account. See instructions for Setting up a Google / G Suite Account.
You can set up your iOS device to synchronize several different Google / G Suite Accounts. See instructions for Setting up Google Account for iOS.
If you are using Gmail or Google Drive applications, you can add several accounts to the applications through the applications own settings.
You can set up your Windows Phone to synchronize several different Google / G Suite Accounts. See instructions for Setting up a Google Account for Windows Phone.