Frequently many sports players will want to see if they can gain further skills or align them better by participating in a different sport. One of the main questions aligns around "does hacky sack help with soccer", more than likely due to both being foot related.
There are a few core skills that Hacky Sack or footbag will help build for soccer players, the first is the building of the eye foot coordination due to the smaller bag size. Additionally it helps you to learn to gain control of your body and positioning that can drastically help you change course while on the soccer pitch.
This doesn't mean that a hacky sack is quality replacement for juggling an actual soccer ball but that it can help you develop those skills especially when you are in areas without the space for normal juggling plus you can carry a footbag basically anywhere and have immediate access.
This is down to the fact that most people develop a high level of hand-eye coordination while they grow up, many of us actually lack a decent amount of coordination between those pecky feet and our eyes and the proof shows up frequently.
One big thing playing hacky sack can do for you is to increase or help your balance. Along with helping you build flexibility, both which are vital to your long term health and wellness on the soccer pitch.
The footbag though forces you to focus on your ability to watch and predict the landing location of the object along with bringing the foot and bag together to either pop the bag back up or to stall it on the foot, both of these translate very well into soccer.
This control is what soccer (or futsal) players want to have and really need to have to be able to get around and through defenders, it is why juggling is a very important skill that they never stop practicing no matter their skill levels.
If you wanted to work on those skills that are directly translatable into your play within a soccer game, play a circle game of hacky sack but with a soccer ball. Get all the players into a circle with about 10-20 feet distance from each other and play the game.
It's not for the faint of heart it will be hard but will deliver you and your team some pretty immediate results to your play.
While it can help with skills for other sports hacky sack is definitely not a perfect match with a normal soccer ball and it may be more aligned to practice with a racquetball or tennis ball.
No matter what though footbag is definitely a good way to practice and to increase your overall hand-foot agility and coordination to help you in all sports which use feet as a primary method of interaction!