I do the following.

When consulting for clients:

  I use an email draft with subject:

    <client name> Tasks done for week ending 7/Feb/2020

       -- task 1

           -- task 1 detail 1

           -- task 1 detail 2

           ...

       -- task 2

           -- task2 detail 1

           ..

When working on own projects:

- I use a physical register

    - Date (at the top)

       - organized notes

       ...

       - random doodling/scribbling

Edit: On a Monday morning, I send that email to myself. So that that week's activities are always searchable by that week ending date. It helps me in my client reporting.