My brother is a physician ~ and he won't even put butter on his toast because of the fat content. I am having a hard time envisioning two doctors scarfing down fast food and shakes as often as you claim.

Physician heal thyself... I gotta wonder what your cholesterol levels are.

At any rate, evening is probably the slowest time and that makes it the best time to clean the machines. It's already been mentioned that health codes mandate that the machine be cleaned every 24 hours. And it sounds like you know this is their routine. Perhaps you could get something else sweet to drink (tea? soda? chocolate milk?) in the evenings to satisfy your sweet tooth.