Hi,
How long has this been going on and how did he first find out that he had protein in his urine?
You can get protein in your urine if you have a UTI, or it could be the beginning of something like nephrotic syndrome that can ultimately lead to renal failure if left untreated. Is his urine frothy at all?
There is another possibility though. If you eat too much sugar all in one go, it is possible to exceed your renal threshold of sugar and if it has happened only the once, then this could be a possibility.
However, get your husband to see his doc and get it checked out.
Sarah