A person may feel satisfied or pleased when they d something bad or unfair to you, but if you can get revenge, you will feel more satisfaction.('He who laughs last laughs best' is also used, and 'he' is sometimes omitted.)
To do something nice or kind to someone who has been nasty to you. If someone felt bad because they forgot to get you a Christmas gift, for you to buy them a specially nice gift is heaping coals on their head. ('Heap coals of fire' is also used.)
If you hear something on the grapevine, you are informed about something by someone, circulating information or gossip from one person to another informally.
('Hear it through the grapevine' is also used.)
When you say that something does or does not 'hold water', it means that the point of view or argument put forward is or is not sound, strong or logical. For e.g., 'Saying we should increase our interest rates because everyone else is doing so will not hold water'.