While there's no direct way to exchange coins for tokens in the game, if you have lots of coins saved up, you can spend coins to replay puzzles to gain token rewards. Tap on a previously completed puzzle square to be prompted to replay that puzzle.

Please note that the game is periodically updated with new features and content that may carry a coin and/or token cost. If you find you have in-game currency in reserve, you may find new uses for it in forthcoming updates of the game.