What are alternative responses for when someone sneezes?
Solution 1:
Both the German gesundheit and the Yiddish zay gezunt (phonetical English transliteration; in Yiddish it would be rendered "זײַ געזונט") have made significant inroads into English. You are more likely to hear the Yiddish in places that had a significant Ashkenazi immigrant population (particularly certain areas of New York City), but both are more-or-less English now (or at least regionalisms). I grew up in a Northern Ontario mining town of about 2000 people with a population that was about evenly split between relatively recent English immigrants and French Canadians who'd lived there for three hundred years or more (with a couple of dozen Italian families and a similar number of Finns) and I was as likely to hear "gesundheit" as "bless you".
I am not aware of any native English sneeze response other that a variation on the "bless you" theme. Well, other than will you cover up when you do that or blow your nose. The old response came from the idea that the soul had temporarily been expelled, and you needed protection until it found its way back. In the time since that superstition died, our attitude toward people spraying germs around the place has become rather less charitable, so it's not surprising that no-one has decided to come up with a "good job" sort of thing in its stead. And I think that our own health has become a greater concern than the sneezer's.
Solution 2:
I don't usually say anything when someone sneezes, as I am not in the habit of blessing people for their bodily functions. However, there are times when I might say, “Get any on ya?” Most people don't get it, though. It bugs me when someone either stares at me or says, “Well … ?” after they sneeze as if I'm obligated to say something. Once when that happened I simply said, “Congratulations!”
Solution 3:
Among friends, a jokey "good one!" is a common response to a loud sneeze.
Solution 4:
If you are among Seinfeld fans, the only appropriate response is "You are so good looking!"