To send a game to someone who won a giveaway I need to add as friend through steam?

If its a steamgift you can send it to email, you will automatically add that person to your friendslist.

If it's a steam gift, you can send it through e-mail too, but that way, you will add him automatically, so either directly or indirectly, you will add him on steam. :P

Thanks to everyone

has someone told OP he can send the gift via mail to the winner?
if not, just letting you know =o,

Well, I send the gift to myself (mail) - copy the giftlink (right click > copy link), paste it in the key field in SG and remove my mail addy before pushing 'send'.
That way I always have the proof that I sent the game.

Example
giftlink before:
https://store.steampowered.com/account/ackgift/1234567RANDOM9?redeemer=me%40outlook.com

gilftlink after:
https://store.steampowered.com/account/ackgift/1234567RANDOM9?