Rodney Hargreaves stretched the advantage with a penalty in the 23rd minute, before his opposite Geoff Berry crashed over from close range after repeated phases to even it up after 34 minutes.
Berry added a penalty before the break, with both sides trading three pointers in the opening moments of a tense second half.
The tide appeared to have turned in Marist's favour when Jamie Davies ran on to a beautiful short ball to make it 20-16 after 50 minutes, but the visitors then failed to turn pressure into points.
A missed penalty from out in front left the door open for Sports, with Honey fresh enough off the bench to burst over to steal it late.
Tauranga Sports coach Stephen Murray was thrilled his players trusted in their systems and had the belief to break out from their own end to steal the match.
"We talked about building a legacy - we are the first Development team to win the competition and we want to set the benchmark," he said.
"You can't ask guys to go out and do any more than they did. We played a really quality side ... they had a great game last week against Te Puke and we knew it was going to be tough."
Murray said the new competition had proved a success. His team was a "real club side" made up of youngsters, premier calibre players and those in between, he said.
"I coached Colts last season and this has been some of the best rugby. I think it's good for Bay rugby and I hope it's here to stay."
Tauranga Sports 23 (Geoff Berry, George Honey tries; Berry 3 pens, 2 cons)
Greerton Marist 20 (Sami Moka, Jamie Davies tries; Rodney Hargreaves 2 pens, 2 cons). Halftime: 13-10.
