The preservative "sodium benzoate" is toxic to cats, not dogs. Sodium Benzoate is in some brands of aloe vera juice. It is NOT dangerous to pets (IMHO). I have been giving it to my dogs and cats for many many years and have never had an issue with it. It had always been a benefit, and my pets tend to live very long healthy lives!
I too give it to my senior cat, George. I buy the reverse osmosis aloe vera juice with the same manufacturer name as my senior cat. I found it in the health food store, but the big online retailer (named after a river in South America) has it cheaper.
My dog Kodi (10 years-old) has had a sensitive stomach and she even has an allergy to gluten so I buy her special dog food without gluten in it. What she has from time to time is stomach gurgles and reflux vomiting. I give her aloe vera juice, which I take also for my digestion problems. I give her 1/4 cup of juice per day until she is better, that is when there is no more hint of stomach gurgles. I have been trying to give it to her on a regular basis, but she does not always want it so I don't force her.