Yes, hamsters can eat grapes!
Hamsters can eat a wide variety of fruits; including grapes.
The only type of fruits that you should definitely avoid are citrus fruits, such as oranges and lemons, as their acidity could give your hamster problems with their digestion.
To feed your hamster grapes, you should first remove the skin, slice the grapes into small pieces (in half at least, preferably into quarters) and remove any large seeds.
Ideally, you should buy seedless grapes for your hamster, as this completely removes any risk of them choking on a large seed.
Before feeding your hamster grapes, you should first feed them a small test piece and check that they don’t show any signs of discomfort after eating it. This will also tell you whether your hamster actually likes grapes – some hamsters don’t!
As long as your hamster likes grapes, and the test piece of grape doesn’t make them ill, then you can start adding more grapes to your hamster’s diet on a regular basis.
This system of adding new things to your hamsters diet applies to all types of food. You should always feed a test amount first to make sure that new foods don’t make your hamster ill – even if you’ve seen other hamsters eat that food with no problems.