Find it hard to believe a mattress can track sleep quality accurately, and in order to aggregate information about your day gathered from other sources and do something useful with it they would need a very complex ML backend, which I doub a mattress company has.
Look at my background, I happen to have been working in big data for the past 10 years. My last job was to run the data platform team of Upsight (former kontagent) the largest analytics and marketing platform for mobile.
Talking about the rest of the team: their background is much better than mine.
Usually a fast means you can drink non-caloric liquids, water being the preference. There are many different kinds of fasts, and some are less strict than others, but for the most part water is allowed in all of them.
