Vitamin C is important supplements for humans as humans cannot produce it on their own.
This type of vitamin however luckily comes in a lot of different foods such as oranges which can easily be consumed and taste great.
On the other hand dogs can actually produce their own Vitamin C and therefore very rarely need a Vitamin C supplement.
So can dogs eat vitamin C or not?
Yes, but it is usually not very necessary as they can produce it on their own.
Ideally it is best to avoid giving any supplements to your dog unless you get the approval from your vet.
However if your vet gives you the go ahead and says your dog needs vitamin C as a supplement it would be fine.
If a dog were to have any serious deficiencies then that may be a case where they would need vitamin C.