Sour grapes is a good phrase to use when someone is criticising something good because they can't have it.
You think my job is too tiring for me because I get to travel abroad too much? No. Your criticism is just sour grapes.
Tony's friends said his new girlfriend was an air-head, but he dismissed their criticism as sour grapes. She was the most beautiful student in his class and they were just jealous.
When you say you have heard something through the grapevine you mean you heard something from someone who heard it from someone else.
I heard through the grapevine that you are getting a promotion. Congratulations!
In the Middle Ages, wine was commonly drunk instead of water, mainly because - unlike water - it was safe.
sour grapes: kedi ulaşamadığı ciğere pis dermiş, tilki uzanamadığı üzüme koruk dermiş
something through the grapevine: kulağına çalınmak, üçüncü kişilerden bilgi almak