The 7-foot-1 Hawes, who is in the final year of his contract, is averaging 13 points and 8.5 rebounds, both career highs, and shoots 40 percent from 3-point range. The 25-year-old Hawes is in his seventh NBA season.
Cleveland has won six straight games, its longest winning streak since March of 2010, which was LeBron James' final season with the team and the last time the Cavaliers made the playoffs. Cleveland (22-33) is in 10th place and three games out of the final playoff spot in the Eastern Conference.
''We have a group that's obviously trending in the right direction and we want to carry that momentum forward,'' acting general manager David Griffin said. ''We feel like this move goes a great length towards doing that.''
Hawes, who is expected to be active for Friday night's game in Toronto, said on his Twitter account, ''Time for the next stage of my career, and I can't wait to get started in Cleveland.''
Center Anderson Varejao has missed the last four games with a sore back. He also missed time earlier in the season with a knee injury and no timetable has been given for his return. Varejao played in only 81 games the last three seasons because of numerous injuries.
Griffin said the trade isn't related to concerns about Varejao's health, but the deal will allow coach Mike Brown to cut down on the veteran center's minutes.
''Anderson gives you everything he has every second he's on the floor,'' Griffin said. ''That's what you love about him, but we also need to be pragmatic about the fact that we need to put a group of bigs out there that can sustain when Anderson sits down. We would like to give him fewer minutes and pair him with things that make his life easier, too. That's what a big part of this is about.''
Griffin, who replaced the fired Chris Grant on Feb. 6, indicated after the promotion the Cavaliers would be buyers rather than sellers at the trade deadline. The Cavaliers were linked to talks that involved forward Luol Deng and guard Jarrett Jack, but both remained with the team.
Deng can be a free agent after the season and it's unclear if he will remain with the Cavaliers.
''I wouldn't be doing my job if I didn't hear what interest there is in our players,'' Griffin said. ''I did that. At no time did we shop Luol. We weren't attempting to trade Luol.''
Varejao, along with guards Dion Waiters (hyperextended left knee) and C.J. Miles (sprained left ankle) didn't make the trip to Toronto.
Clark is 6-foot-10 and can play both forward positions. The five-year veteran, who signed a one-year contract with a club option in July, is averaging 5.2 points in 45 games. The 6-10 Sims is averaging 2.2 points and 2.8 rebounds in 20 games. He's in his second season in the league.
The Sixers (15-40) have lost nine straight and 19 of 22.