The 20-year-old Harris appeared in 42 games last year, including nine starts, during his rookie season. He averaged 5 points, 2.4 rebounds and 0.5 assists in 11.4 minutes per game. The Bucks exercised the third-year contract option on Harris.
The 23-year-old Sanders played in 52 games last season and led the Bucks in blocks with a total of 76. He also averaged 3.6 points and 3.1 rebounds in 12.4 minutes per game.
Udoh split time between Golden State and Milwaukee last season, appearing in 61 games, including 11 starts. The 25-year-old Udoh averaged 5.6 points, 4.2 rebounds and 1.6 blocks in 21.2 minutes. The Bucks exercised fourth-year options on Sanders and Udoh.