a good substitute for pineapple when cooking a ham
Pineapple brings a touch of acidity, sweetness, and general fruitiness.  I am going to assume you would have been using canned pineapple, so the enzymatic action is not really a factor (and it would be stopped as part of the cooking process).  It is also hearty enough in texture to stand up to the baking.

For the juice, I would recommend basic orange juice, perhaps cut with a little extra lime juice for complexity and acidity.  For a fruit garnish, peaches (frozen or canned since it is not peach season) should work quite well.

If you can find good mango, that would also work very well.

This application is very flexible and forgiving.  With the soda, and the cherries, you could even omit the pineapple part entirely, and still have a good outcome.