What can you use the coins for?

As far as I can tell they are useless except to purchase different themed or colored backgrounds. Beyond that, stupid coins.

I've been playing Water SortPuz for well over a year, and I still have no idea what the coins are for!

Played 500 games have 20k in coins. And thats after I bought all available wallpapers, bottles and colours. Pointless.

Can the person who is disagreeing with these answers please explain what the coins are for?.

Lol. And the wheel spin. Which has more coins as a prize. So annoying

Coins are only for buying backgrounds etc. But I woke up and my water sort has changed. Now there is a prize box that you have to fill and claim, so you van level up. I am on level 9093 and I am right at the bottom of the leader board with 656 trophies level elder. At the top of the leader board is 25810 trophies at viceroy level. Do not understand how they got all those trophies when the leveling up has only just been added.