Apple’s free App of the Week is WaterMinder, a $3 USD app that reminds you to drink water:
Get help with WaterMinder®, an easy, intuitive app to track your water intake. Based on your body weight (or your personal goal), WaterMinder® will remind you to drink water to reach your daily goals. By seeing current water fill visually and in percents you will instantly know how well you are hydrated!
The app has a simple interface, has pre-defined cups for water tracking (or any other beverage), or create custom cups and reminders, in either Imperial or Metric units. It also has HealthKit integration to share water data to Apple’s Health app, and was recently updated to sync to Fitbit accounts.
Click here to download WaterMinder in the App Store while it’s free for the week. It’s a 90MB download and also supports iPad and Apple Watch.