Here is the full list of all 7 SnOut achievements.
Hit the ball with your snake 40 times without it touching anything else
Lose to a ball that's just bounced off your snake
Break every block on the board
Play a game that lasts longer than 10 minutes
Pick up a coin with a value of 10
Achieve a score of 100 or more
Earn 666 coins (or more) in a single game