On the free app there's no login, so there's nothing to sign into or out of, your data lives on your device.
If you tapped a "sign in to a business account" option and it didn't work, that option is for ToolBerry Pro (our team version), not the free app.
Want to clear everything and start fresh? Go to Settings > Advanced > Factory Reset. This wipes all data on your device, so back up first if you want to keep it.