https://www.polygon.com/2019/2/21/18235215/apex-legends-rewards-without-twitch-prime-how-to

Apex Legends partnered with Twitch Prime to give players Apex packs and an exclusive skin, but it turns out you don’t actually need Twitch Prime to get the rewards in-game on PC.

Players have discovered that by opening the game’s settings in Origin on PC, they can edit the advanced launch options. If the command, “+twitch_prime_linked 1” is added, Apex Legends will reward players with the five free Apex packs and the legendary Pathfinder skin the next time the game is opened.