Dailies, also referred to as the daily challenge or streaks, is a big daily coin reward for playing minigames.
Every consecutive day you complete your daily challenge, your streak increases. The higher your streak, the higher your coin reward. There is no hard limit on how high this reward can grow, making it the biggest source of coins by far. Completing the challenge takes ~20 minutes of minigame gameplay.
There's a leaderboard located in the hub for the highest streakers of all time. The Loyalist badge is unlocked at streak number 15.