>>121937546it's either Banana or Pineapple, as those are two of the oldest Ice Cream flavors & toppings(after all look at the toppings on a classic Banana Split and compare to the known 3 Flavors and my two guesses), also considering two of the four flavors are bean based(Chocolate & Vanilla), it makes sense the Fourth Flavor would also be a Fruit to match with Strawberry
Lemon is also a possibility since it used to be a really popular flavor in the early days of Ice Cream, but probably a distant third compared to Banana and Pineapple
