Setting activity variables from different activity

I have some major variables in my main activity that I retrieve their values from internet once the user log in. after that, there are multiple activities that can alter these values in the database but this doesn't reflect in the current loaded values until the user log out/in. (the process where I retrieve data from internet)

what is the best way to update these values in main activity from activity 2 directly without logging out/in?

is there a way to set these variables without making intent and putting the new values in extra bundle? ( I need to change the values without returning back to the activity)