If you are talking about buying stuff for friends then this is the way. Else if your talking about giving a-coins that your friend already has then not possible.

Tell him to get the player he wants to transfer to ID.

Then he can go to store, select the a-coins/credits and press give as gift then enter the player's ID.

Hello! Thanks a lot for sharing your idea with us. At this point, we don't consider any exchange or trade system. Stay with us, as we will inform you if we decide to make any updates in this regard in the future.

However, you are welcome to use the Mech Arena Store: https://store.plarium.com/en/mech-arena/ 🛒

With its help, you can send Resources to your friends 😉