Use plastic cups to build castles and towers. This will help with fine motor skills, precision and basic notions of architecture. When finished with that ideea find a pin pong ball and play where is the ball. Just shuffle the ball between cups then ask them to guess where the ball is. As my little one found shuffling with three cups difficult she decided to shake two cups to hide the ball for me to guess.
There are several other ideas to play with cups and balls: cup bowling, target practice, catch. The list is endless.