[thecodont]

There is a sure fire way to tell if a tomato is sweet or not (short of tasting it or cutting into it). What is that method?

Well, if squeezing out a drop of juice doesn't count as "cutting into" then this is certainly a good method.

https://www.youtube.com/watch?v=LpXfTuChlKQ

[poconopundit]

My wife is Japanese and she taught me that a sweet tomato has a peculiar smell if you hold it close to your nose.

You need to learn the smell, but the best I can describe is that it’s an earthy smell. Very distinctive.

So this knowledge is relatively unknown in this country.