I use a regular ethanol content sensor ($30) and it plugs into a device from fuel it ($200) that is then read via Bluetooth on an app ($5) on my phone. I would highly recommend it. I literally copied SBS's model from the link below. The only word of caution I would say is that after you fill up, it takes a while 5-15 minutes before the gas mixes properly. I always put E85 in first, then drive across the street to another gas station to put the 93 in. The E content will go up for a few minutes, I've seen as high as mid 40's. I just drive it real easy until it comes back into the 30's.
It is a very noticeable difference from a 93 tune.
https://www.ecoboostperformanceforum.com/index.php?topic=9790