DH just been diagnosed with diabetes

Dh has been lacking in energy , motivation and general get up and go, for the past year. He had a TIA last April 2020 and really hasn’t been right since.
Had a full blood test last week and the doc phoned to say his VitD level is down and his sugar levels are high. I’m not surprised as he has a very sweet tooth. He needs to see the nurse now for advice and diet recommendations,
Just wondering if any grans have diabetes and any dietary tips you might have. Everything seems to have sugar in it.