To preface this: this is not fun and not a glitch; this is a slow painful way to make roughly 150k+ a week using All American Solo Seasons. I recommend watching a show or something while doing this to make it less mind numbing. It will take you 60 to 80 minutes a day.
Here is the method:
Play 1 All American Solo Season per day
8 games undefeated, games take 7 to 9 minutes each
5500 coins per 5 win regular season + 450 coins per individual win
5500 coins per 3 win playoff (1 game bye if undefeated) + 850 coins per individual win
1400 coins per National Championship win + 2 FG Packs (Alternatively, you can lose this game for 4k coins)
Total: 17,200 coins guaranteed + either 4k straight up or 2 FG packs which will average out to a little more, we will say 6.5k conservatively
So 23,500 per run, 165k for 7 to 9 hours, 1 hour a day + excess
Tips for games:
Chew clock, jet touch pass flipping back and forth, you can let the AI run the ball for you
Either chew the entire clock in both halves trying to keep the game tied so the opponent won't use TO, and than kick walkoff FG, or take the lead and just chew clock, ultimately kneel once they've used TO so clock will auto run out.
Also gives you a chance to hit XP milestones if you would like, but will slow your pace. In no way am I suggesting this is the best way to make coins, but it is free and effort free.