How do you give gift cards to people in hay day?

You can send thank you notes (letters) to the people who help your farm when filling crates on your boat, or by watering your withering Trees and Bushes. You just need to tap on their avatar to revive the dead plant they watered, and then tap on their avatar again to send the thank you note.

The avatar will have a little envelope showing so that you know you're sending a thank you note to that person. A message will also appear briefly on your screen, and it reads something like "you have sent a thank you note to *****". You only get a little time to do this as the avatars disappear pretty quickly after you have tapped them the first time.

When your boat crates get filled, you only have to click on the crate/avatar once I think.. Hope this helps :-)

Ps - Not every thank you note contains a gift card. A person can receive unlimited thank you notes per day, but only a maximum of five gift cards per day.