Soften frozen yogurt on countertop for 10 minutes.
Meanwhile, combine chocolate syrup, coffee granules and 1 tablespoon warm water in a small bowl.
In a large bowl, beat frozen yogurt with 2/3 cup of the whipped topping until good spreading consistency. Place half the ladyfingers on bottom of an 8 x 8 x 2-inch baking dish, spreading to cover as much as possible. Drizzle with 2 tablespoons of the chocolate mixture. Working quickly, spread with 1 cup of the frozen yogurt mixture. Top with 1 cup whipped topping. Repeat layers (ladyfingers, chocolate sauce mixture, frozen yogurt, whipped topping).
Dust top with cocoa; cover with plastic wrap. Freeze at least 4 hours or overnight. Let soften slightly before serving.