What fruit can guinea pigs eat?

Fruits are, in general, not good for guinea pigs because they contain too much sugar and are not part of their natural diet. Therefore, Guinea pigs must always have hay available to munch because it is the part of their natural diet that they need. 

Vegetables like carrots or peas are much better, and they can have up to a cup of vegetables every day.

Don’t forget, guinea pigs are not humans and don’t know what they miss if you don’t feed them fruits.
Fruits should stay a rare treat. The best choices are low-sugar fruits like blueberries, strawberries, or a piece of watermelon. A half apple or 1/4 banana per week should be fine. Fruit should not make up more than 10% of their diet.

However – once again: Your guinea pig must always have hay available to munch because it is part of their natural diet that they need.