Problem
So you let your friends who didn't bring their phone to the bar, log in to your phone, and now you get all their notifications. What to do?
Solution
Whenever you let someone else log in to their account on your phone, you basically register your device to receive their push notifications. To get this to stop - you need to have them go to their settings (https://untappd.com/account/connections) and remove your device and the push notifications will stop.