BigDrink ships a companion Apple Watch app, not just a mirror of the iPhone screen. The app's own FAQ sums up what it's for: quickly check today's progress through the watch face complication, record water intake directly on the watch, receive reminders, and view today's stats — all without touching your phone.
The Watch app's own screens use plain, direct labels — "Add Water", "Water Records", "Today's Goal" — so there's not much to explain about the interface itself. The useful part is knowing where those screens live and how the complication gets on your face.
Steps and screenshots verified against app version: 1.0.4
1Install BigDrink on your Apple Watch
If it didn't install automatically alongside the iPhone app, open the Watch app on your iPhone, find BigDrink under Available Apps, and install it. It shows up as its own app on your watch, not a shortcut back to the phone.
2Log a glass with Add Water
Open BigDrink on your watch and tap "Add Water". Pick one of the preset cup sizes (Small, Medium, Large, Extra Large) or use "Custom" to enter an exact amount in ml. The entry syncs back to your Water Records like any other log.
3Check today's goal and history
"Today's Goal" shows how close you are without opening the phone. "Water Records" lists every entry logged today, from either device — tap one to delete it if you tapped the wrong amount.
4Add the BigDrink complication to a watch face
The complication is called "BigDrink" and its description is "Today's water progress" — that's the one to look for. Long-press your watch face, tap Edit, swipe to the complications layer, tap a slot, and pick BigDrink from the list. From then on your progress is one glance away, no app launch needed.
The watch app, the complication, and your iPhone all read from the same log — there's one water total for the day, not separate ones per device. Reminders can fire from either side too, so pick whichever device is more likely to be on you.