Taronga Zoo's tea-drinking orang-utans choose herbal tea in Sydney
"They love it - we try to keep enrichments random so they don't get bored," Ms Marshall said.
"It's also a good way of ensuring they stay hydrated."
GALLERY: Take a look at the playful primates on The Mosman Daily
Jantan, a male and Willow, a female, recently moved back into their newly refurbished exhibit after two years in an off-display facility while developments were taking place.
The pair, who are not a breeding couple due to their hybrid status (Sumatran-Bornean), are slowly readjusting to their new surroundings and building trust in their environment.
"It's been a big change for them - Willow is a bit naughty, she's more reluctant to come out," Ms Marshall said.
"Willow's more cheeky and dominant, she likes to be in control whereas Jantan's more placid and laid-back."
She added her biggest fear was that the stress of the move might affect the primates' appetites and general well being.