This is a team activity suitable for about 6 people. They need to know the alphabet, and can get progressively better as they learn to work as a team, and get the method right. I came across it used for adults, but children can do it too as the rules are so simple.
Tape or rope to mark out a square on the ground.
The letters of the alphabet written on printed on separate sheets of paper.
Lay out a square on the floor, probably about 2m or 3m on each side. Put in this square the 26 letters of the alphabet on separate bits of paper, face up, so the letters are visible, but mixed up randomly. Make these nice and large - a post-it size is ideal. I have laminated some for re-use.
The objective is for all the letters to be touched in alphabetical order as quickly as possible (use the stopwatch to time). The one rule is that only ONE person is allowed in the square at any one time.
Tactics play a big part in this. One person can do it alone, but they will be slow, as it is hard to remember where all the letters are. In a team you can either assign the letters close to each person to them (the team can stand around all 4 sides of the square). but that can be hard, as there is lots of hopping in and out of the square. Another option is to assign A-E to person 1 and F-K to person 2 etc so that person only has to remember the location of a few letters.
You can start with a flat time limit of 60 seconds, or you can make it competitive and see which group can do it fastest.
To use for a team-building activity, don't give them clues about how best to do it, but let them try a couple of times, then challenge them to discuss what worked, and what didn't work, to come up with other options to try, and to see if they can get any faster.