In 15 minutes…
Beginner athletes: Double Unders, using flight simulator rep scheme.
Intermediate athletes: Muscle Up progressions…
Ring muscle transition on low rings.
Kip swing from high rings.
Box jump muscle up on high rings, from box.
If appropriate and time remaining, single attempts at ring muscle ups.
Advanced athletes: Incline/Decline Handstand Walk, using plates. In this particular case, advanced athletes are considered ones that routinely perform ring muscle ups in workouts without modification to the movement or rep scheme. Additionally, if you can perform them, but do so with less than desirable technique, you should consider taking time refining your technique.
25 American KB Swings, 53/35
25 Lateral Jumps Over KB
25 KB Floor Press, 53/35
25 Ab Mat Sit Ups
30-50 Weighted Ring Dips (adv) or 100 Push Ups (beg-int)