Cole had fallen behind the likes of Kenwyne Jones, Anthony Stokes and Michael Chopra in the pecking order at the Stadium of Light, making only eight appearances this season.
And the arrival of Swedish international striker Rade Prica has forced the former England international to look elsewhere for first-team opportunities.
But Coyle has no doubts about Cole's qualities: "He's still hungry to score goals, he's got a point to prove and that's the type of player I want to bring to the football club.
"There's not an ounce of body fat on him. He's been a top professional all his career and that's why he's had a distinguished career because he's looked after himself."