Angel Food Cake: crushed pineapple instead of sugar?
Sugar is not used as a sweetener in cakes, it is a major component which creates the needed texture. As such, it is very difficult to impossible to replace. 

In angel food cake, you absolutely cannot replace it. Angel food is a fragile cake without chemical leaveners, and depends on a very well balanced ingredient list. Using a fruit puree instead of the sugar will create a mess. Also, the tube pan is important for angel food cake, unless you are willing to bake very thin separate layers, else the cake won't bake properly. 

If you really insist on replacing the sugar, the least risky base would be a pound cake, since it is relatively insensitive to extra moisture. The basic ratio there is 1:1:1:1 of eggs, sugar, flour and butter by weight. If you are extra careful in reducing the moisture of your puree - maybe drying the pineapple in a low oven for several hours after it has been pureed - you will likely end up with something edible. It will be quite far from the original, and it would be better classified as a fruitbread than as a cake, but at least it is likely that it won't bake into a brick or remain a sticky underbaked mess. Other types of cake won't be as forgiving.