Something I often lack in my day is water so I am trying the Waterminder app. It has a suggested daily intake due to your weight and activity. You can then program cup sizes that you normally drink. For example a grande at Starbucks is 470ml. All liquid counts but water is the most recommended.
There are achievements to unlock and constant reminders throughout the day to remind you take sips. They appear on my Apple Watch too, which can be a tiny bit aggressive. At least now I have no excuse not to drink more water!