If a female has a vaginal yeast infection can the guy get it if she gives oral sex?

Unlikely: If a woman has a vaginal yeast infection, it is unlikly that a man will develop an infection regardless ot the type of sexual encounter. Most women have some yeast present vaginally. Yeast is considered an infection when a ph balance or change in balance of natrual flora leads to an overgrowth of yeast.

No: If it is caginal yeast and she performs oral sex on him there is no possible way for the yeast to be spread.