Line a 4-quart round mixing bowl with parchment paper.

Break angel food cake up into small bite-sized pieces. Pour pineapple syrup into a 1-cup liquid measure; add water to measure 1 cup if needed.

Dissolve gelatin in cold water. Add boiling water, pineapple syrup, sugar, and lemon juice. Mix well and refrigerate until just starting to thicken.

Stir crushed pineapple into gelatin mixture, then fold in 4 cups whipped topping.

Place a layer of cake pieces into the prepared bowl, followed by a layer of pineapple mixture. Continue until cake and pineapple mixture are used up. Refrigerate for at least 12 hours.

Turn chilled cake out onto a serving platter. Frost with remaining whipped topping and sprinkle with coconut.