Many people here suggesting a throwaway email and/or VPN. While this does migitate the impact somewhat, the only proper response is to not use their "service" and deactivate the WiFi fo your phone (else they might be tracking your MAC address).
Walmart has an interesting app where if you're connected to their wifi then the app "transforms" to tell you what's in stock in the store you're connected to. I wish they'd just do something like Home Depot where the site just tells you if X location has an item or not, but alas.
Wait, do they not do that anymore? I used to be able to search on their website for an item and it wold tell me if it's in stock at the store I selected and the aisle it's in if they have it.
Android has allowed you to randomize your mac for a long time, and is currently the default setting. In developer options you can even toggle a setting to enable non-persistent randomization.