When you finish games, you get a random fruit fact on the same screen where you get your stats for each round. You must have been given three strawberry related ones at some point in time. The strawberry ones seem to be more rare than others (which might be related to the fact that they are an achievement).
In some versions, there are arrows on the screen that let you change between views (so you can actually see the fruit fact you get at the end of the round).
It will look something like this (this particular shot is from the iOS version):
