Any item that you child enjoys using or playing with
This activity is an "everyday/anyday" activity. Although the child might not understand entirely what "taking turns" means we are always verbalizing our interactions when we are together
When we notice he wants to get involved with what we are doing or using we verbalize it. "It looks like you would like a turn too. First its mommas turn then its Theo's turn." Then as soon as we see him calmly waiting, we follow up with "Ok I'm all done its Theo's turn now" and then hand him the object.
As we continue doing this, I notice he willingly "shares" and knows that we follow through with what we say. This makes him more willing to wait. It is important that if you say something you follow through with it.
It's best to do this when you notice they are performing the behavior you desire because then every time you say these words to them they know what you expect and what they need to do to get a turn in return.
Your child might not fully understand what we are showing them and implementing but we are setting the standards/expectations. This sets up a successful time later when interacting with others.
This does not have to be done as a sit down activity. Incorporate this into daily life. We do this a ton when Jesse plays the guitar because he is os interested in touching the guitar. You can practice this skill anytime!