Originally from Palmerston North, the family usually spent summers in Riversdale, where they own a bach.
A cafe in Riversdale Beach was long overdue, Miss Donaldson said.
"We've said it for ages and everyone's said it -- we really need something out here ... there's nothing else out here for day trippers." After seeing the success of the pop-up container shops in Christchurch, a container cafe seemed like a perfect fit for the new business, she said.
"It's something that you can start small and build on.
"It's just a cool concept -- I didn't really like the standard coffee carts and these do really well in the weather -- they're pretty sturdy."
Specialising in organic Fair Trade coffee and home-made treats, the cafe sells as many as 200 coffees a day.
"I had no idea that people drink that much coffee. We have a lot of locals who come down every day, twice a day."
Miss Donaldson, who was formerly a naturopath, wanted to make the cafe as eco-friendly as possible.
The cafe uses biodegradable cups and all the furniture has been made from recycled crates, pellets and doors.
"I wanted to have things that are a little more forward-thinking."
If this summer continues to prove a success, she plans to expand the cafe next year, adding more products and live music.