What are their sponsor names?
SELECT T3.Sponsor_name FROM player_coach AS T1 JOIN coach AS T2 ON T1.Coach_ID  =  T2.Coach_ID JOIN player AS T3 ON T1.Player_ID  =  T3.Player_ID
their refers to a group of entities previously mentioned or understood from context; sponsor names refers to Sponsor_name; involves joining tables (player_coach with coach, and player_coach with player) to retrieve the desired information.