I’ve always used the Oxbow commercial treats, specifically the veggie and barley. They are basically ground hays and dried vegetables and are fine in limited quantities. (No more than 2 a day.)
There are also some natural treats sold in the BB store that my bunny loves, and I feel are quite safe. They are like homemade baked treats, with careful ingredients that are good for bunnies, similar to those used by Oxbow, and no additives. BB is careful to screen the products sold in her store, and sticks with really healthy ones.
Some members have even posted recipes for simple, home made treats that are like tiny cookies. They are very healthy, since they also are made with basic ingredients.
Raisins are good too, if you don’t have any craisins.
Very tiny quantities of fresh fruit, like an apple slice or a 1/4 inch piece of banana will be very tasty to your bunny also. I’ve never tried the Purina.