How do I edit or delete something I logged?

Right after you log something on "Overview", the note under the card lets you "Undo" it or "Edit" it. Later, tap "Browse", then "My log" under "Health Tracking", and pick the day: tap the trash can to delete an entry, or the pencil, where there is one, to edit it. To remove a drink you logged, swipe left on it under "Today" in "Water".