Credit for this solution goes to Sashamorning from the Madden 18 achievement.
I can confirm this still works but fumbles are much less frequent than they used to be in the previous games, especially when using the hit stick RB seems to be the better method now. I find it better to use a linebacker than a DB as suggested below but its personal preference:
Very doable, but a serious PITA.
This works best with 2 controllers. This works best in arcade mode.
Set your team to rookie difficulty and the second controller to All Madden
First, go into Settings => Player Skill => Fumbles => 0 (NOT 100). You want the second ("human") controller to drop the ball.
The main controller selects something to pull the defense back. I used Dime => Prevent.
The second controller uses Special Teams => Fake Punt W Release
Your main controller should select a defensive back (not a lineman, they don't like to do this) and move them right next to the punter.
When your 2nd controller snaps it, they're going to hold on to the ball. Take your main controller and go after the QB. You're going to find that the player is strangely not interested in sacking the QB, so hold him to it, and MASH RB. With luck, two things will happen:
1) Your defenders will STAY AWAY, or at least as far as possible.
2) Your player will strip the ball. This almost always happens. The annoying thing is that either one of your teammates or an offensive lineman gets there first. There really is luck involved here.
If this doesn't work, don't fret! You can do it again! Forever, if need be (and it will likely feel like it). Since you were offside, the offense will be able to accept or decline the penalty. ACCEPT it, and you can immediately try again.
Once again, ACCEPT THE PENALTY, so you can try it again. The line of scrimmage will end up moving all the way down the field toward the end zone, but will stop. That means you have endless tries until you either get the achievement, or break your controller. Hopefully it's the first one.
Edit 1: when you are finally successful make sure you decline the penalty with player 2s controller. The achievement will not pop until you do so.
Edit 2: Credit to NoHeroes94 in the comments. If you press A and Up on LS with player 1 it will hold the defensive line in position so you only have to worry about the offensive line trying to get the ball back.https://gameclipscontent-d3023.xboxlive.com/xuid-25332748196...