i afk'd my way to battle pass tier 100, its pretty simple
start warzone
go to options, bottom of first page, disable auto deploy parachute
turn off fill team and start Plunder
walk away.
you just drop to your death every minute, it auto requeues for a new game when its over. It does NOT effect your KDR in warzone.
It earns about 1 tier every 30 mins so its slow as fuck, and I'd do it over the day as sometime during the night it does a game tweak or something that disconnects you. It took me around 10 days of AFKing 8 hours a day (on ps4) to go from 1 to 100.
yeah its dumb as hell but what the hell, I don't even care about skins (still using all defaults) but its nice just earning everything for the season. Honestly the only reason its still installed is because I really do enjoy the last few weeks of a season when they bring back shipment 24x7.