I use fruit in my cupcakes sometimes and I pull them out of the oven and they look great, but as they cool, they sink. Why and what can I do to stop this? Too much fruit? Add more flour? Help, and thank you in advance.

They may be underbaked. Fruit contains a lot of water, so try adding extra flour to the batter and bake a few minutes longer.

when I added strawberries, they did the same thing.... I agree with adding a bit of extra flour and baking longer.