(Pardon me if I don't make sense. I typed this out once and then my computer erased it. Plus I haven't slept in a very, very long time and can't see my monitor so well anymore. Stupid finals.)
Freeze-dried foods have been referred to as "cardboard" by some people. Others seem to think it's a good food option. I've fed it to my fish and never had any problems. They've loved freeze-dried brine shrimp and bloodworms. But they love the frozen stuff a lot more, so I usually give them that now as treats. Especially since I ran out of freeze-dried brine shrimp, and my cats ran off with my freeze-dried bloodworms and I haven't seem them in weeks. I used to powder them up into a powder-mixture for various smaller fish.
A better treat is really frozen stuff. The prices are usually somewhat comparable. I've noticed my frozen stuff tends to get eaten with more exuberance than the freeze-dried stuff.
Should be able to get a 2 ounce package of frozen brine shrimp at Petsmart or Petco, or most LFSs for about $2.00. It can go a long way if you feed small portions, which is all the Bettas should be getting as a treat, anyway.