"Furosemide works by blocking the absorption of sodium, chloride, and water from the filtered fluid in the kidney tubules, causing a profound increase in the output of urine (diuresis). The onset of action after oral administration is within one hour, and the diuresis lasts about 6-8 hours." Source - MedecineNet
I've had thrush once and a stomach yeast infection once, both times it was after a course of strong antibiotics. The theory being that wiping out all the bacteria, good and bad, allowed a yeast infection to take hold.
I can only imagine that passing a lot of water and my memory of Furosemide is that there's a lot of that soon after taking the stuff, might prevent yeast infections from taking hold. Only guessing mind.