Here is the full list of all 43 SWEATER OK achievements.
Destroy 10 snake parts
Smash 10 eggs
Collect 3 stars during the slow motion
Allow snake to eat a black mark
Survive for 1 minute
Allow snake to eat a speed boost
Collect 10 stars in a single session
Gain a 10x multiplier
Collect less than 100 points in a single session
Collect 50 stars in a single session
Collect 100 stars in a single session
Collect 100 stars
Collect 500 stars
Collect 1 000 stars
Collect 5 000 stars
Destroy 50 snake parts
Destroy 100 snake parts
Destroy 5 snakes simultaneously
Destroy 10 snakes in a single session
Collect 50 000 points in a single session
Collect 100 000 points in a single session
Collect 500 000 points in a single session
Collect 1 000 000 points
Collect 5 000 000 points
Collect 10 000 000 points
Allow snake to split into 20 parts and kill them
Allow 10 snakes to appear on a level
Smash 100 eggs
Smash 1 000 eggs
Smash 228 eggs in a single session
Allow snakes to eat 100 stars
Allow snakes to eat 250 stars
Allow snakes to eat 500 stars
Die 666 times
Survive for 5 minutes
Survive for 10 minutes
Survive for 15 minutes
Survive for 30 minutes
Survive for 45 minutes
Survive for 60 minutes
Allow snake to kill you during a speed boost
Fail to collect the black mark (you need to be closer than 3 tiles from it)
Play 69 times in a row