Here is the full list of all 12 Sausage Fest achievements.
Get a kill for the first time in any game mode.
Get 5 kills in a match for any game mode.
Get 10 kills in a match for any game mode.
Kill an enemy with your ult in a match for any game mode.
Kill 5 enemies using your ult in a match for any game mode.
Buy any Sausage skin from the shop.
Buy any Bread skin from the shop.
Buy any Kill Emote from the shop.
Buy any Rocket Trail from the shop.
Have 50 mystery jars.
Have 100 mystery jars.
Have 250 mystery jars.