You could have a sticker chart, and they put on a sticker or a sta,p when they stick each routine and when they hit a certain number get to do some,thing fun, like a fun new skill drill. You could also do this as team and once the team hit a certain numeber of stuck routines, they all play a game.
They could take turns to video each other so they can watch their routine and give themselves say three pieces of feedback.
Split them into teams and each time they stick a routine they go and get a peoece of foam pit of the pit and put it with their team mates and the tallest pit foam tower wins.
I've played a game where the girls are broken into 2 teams (I make them so they are pretty evenly matched) and for each event I pick 3 specific things I'm watching for- they get 1 point for each.
So for beam the 3 things might be 1. controlled finish on turn, 2. meeting split angle requirement, 3. stuck dismount. For each one they successfully do, they get a point. When they finish their routine I give them their point total and they mark on their team whiteboard. Sometimes I'll even go through the 3 things with the team after each routine to get them watching for specific details in routines. Then we total them up at the end. The winners don't really get anything, but sometimes I will let each of the members of the winning team get 30 seconds on the trampoline instead of splits at the end of practice or 5 less of something we're doing for conditioning.
I've also done the same thing but as a whole group and we set a goal number for each event. So say there are 10 kids, 3 possible points on each routine so a max of 30 points. I'll knock a few points off of that and make the team goal something like 25. If they meet it they can move on, if not we go back and work on whatever the problem area was.
I've also had them watch their teammates and after each routine tell the gymnast 1 thing to work on and 1 thing she did well. This only works with a group of kids who are pretty kind and conscientious. At my old gym my kids were super sweet and encouraging to one another and it worked well. With my current group of kids it would be a disaster.