I roasted beets tonight (fresh -- I don't do canned -- with a spritz of olive oil and just a bit fresh-ground sea salt) and dropped a piece on the floor when I was putting them on the dinner plates. One of the puppies snapped it up in a flash and trotted away with it and munched happily... I gave the other pups a small piece and they loooooved it.
But I've heard beets aren't good for dogs because of the sugar content? or is that just when they use beet pulp as a filler in cheap dog food? I'd like to give them some more tomorrow as a treat, but is that safe? I did a search but can only find where beet isn't recommended in dog food but haven't found it on any "dangerous to dogs" lists.
I think it's only bad when the dog has to eat it every day, a little extra won't do any harm. Depending on your dog, you could feed a bit less tomorrow morning or tonight so that he does not eat too much but that's it.
Dogs are pretty resilient. After all, they're descended from scavengers and will eat almost anything. Beets (occasionally) shouldn't hurt them (might get loose stools for a while from all the sugar). I used to have a dog that thought onions were God's gift to canines; he would dig them out of the garden and eat them.