Ehhhhhhhh. It really depends on what type of toppings. My cheesy onion and pepper focaccia works beautifully as croutons. It takes a bit longer to dry out because you've got to get the peppers and onions fully dried too, and is best used within 2-3 days. But a focaccia with a lot of wet or large toppings like tomatoes or olives or figs or whole garlic cloves would be a bit trickier to use for croutons. You'd want to remove as much of the toppings as possible before cutting it into crouton pieces.