http://www.espn.com/espn/feature/story/_/id/25316231/health-inspection-reports-find-critical-violations-nfl-nhl-nba-mlb-stadiums-2018-espn-lines#!
To be clear, there are no rankings for the cities, but in looking at all MLB, NHL, NFL and NBA facilities across the country, Miller Park is #1 among MLB stadiums (#7 overall) and the BC is (was) #3 among NBA arenas (#4 overall)... a cursory review of the top 10 shows that only Phoenix has two entries (State Farm at #8 and Gila at #10), so if you look at average overall rank, Milwaukee is, by far, #1.
That doesn't mean it's good food or won't make you sick... it just means there are fewer high-level health code violations in Milwaukee.