The Deal
Cavaliers get: Rights to forward Albert Miralles
Bucks get: Guard Matthew Dellavedova, cash considerations
Cleveland Cavaliers: A

With the Cavaliers unwilling to match the four-year, $38 million offer sheet Milwaukee was prepared to give Dellavedova, he was headed to the Bucks either way. The point of this sign-and-trade was entirely to benefit Cleveland using some creative work with the salary cap.
Because Dellavedova is getting a raise larger than 20 percent and is being used in a sign-and-trade deal, he counts for only half his 2016-17 salary of $9.6 million for trade purposes. By trading him and getting practically nothing in return, the Cavaliers create a trade exception in that amount ($4.8 million), which is convenient because that happens to be almost exactly the size Cleveland needs to take in Mike Dunleavy (making about $4.8 million) as part of the team's trade with the Chicago Bulls on Wednesday night.
Using the new Dellavedova exception on Dunleavy allows the Cavaliers to retain their entire $9.6 million trade exception from the Anderson Varejao trade. While it's unlikely Cleveland would want to add that much more salary to what's already an enormous luxury-tax bill, the flexibility is useful to have and it cost the Cavaliers only $250,000, according to ESPN's Brian Windhorst.
Milwaukee Bucks: B

Dellavedova was a natural fit for Milwaukee because of his ability to defend point guards while playing off the ball on offense alongside Giannis Antetokounmpo. Dellavedova could even start in that role, which would make him a good value at a little less than $10 million a year.
Other than what the Bucks are getting in the deal, the main effect of this trade -- as opposed to signing Dellavedova as a free agent -- is that by receiving a player in a sign-and-trade deal they are now hard-capped at the luxury-tax apron, $4 million more than the tax line. That shouldn't be an issue for Milwaukee, which has some $25 million or so to spend before reaching the tax and surely wouldn't pay it this year either way.
The player Milwaukee gave up, Miralles, was selected in the second round of the 2004 draft, is now 34, plays in Spain and has no NBA potential.