How do you create a visual that updates with sales throughout the day

I think there are a couple of different ways you could approach this.

You could build a workspace project for the current day and breakout by hours so you could see the key product sales volume throughout the day.

Depending upon the audience, this could also be a good use case for a mobile scorecard.

Here are example screenshots for each approach with demo data.  Also note that the data in Analytics has a delay, typically around an hour. 

In addition to the point about the 45 min delay to process data, you might want to use some custom date logic to only show up to the last hour of the day, and maybe compare the previous day up to the same hour.

You can set you "current" date range to:

And if you are comparing to yesterday, you can add a custom date comparison of:

This will at least hide all the empty rows, but that last hour of today may still be partial data due to the latency.

But at least I am not comparing the full yesterday to the partial today, and when not comparing you won't have all the empty rows that haven't happened yet.