Hello WesMerta we’ve been trying to find the best solution for your case. There are a couple of things you could do.
1. You could directly share your the spreadsheet with your employees, as long as you set the General Access as Anyone with the link can Edit. But this will leave your spreadsheet open and you won’t have a control over who is adding each data.
2. A second solution would be to ask your employee to associate their Yahoo address to a Google one, like this they will be able to access the spreadsheet on Google Drive using their Yahoo emails. You can check this google documentation about this option.
3. A different solution would be to create a form link to the timesheet spreadsheet. You can share the form link with your employees, they don’t need a Google or Sheetgo account to fill out the form. With the form, the information will automatically populate the spreadsheet.
These are some possible workarounds, let me know which one best suits your needs :)