A sow and one of her cubs entered the back of the van, which had its back doors open as its driver was making a delivery to a convenience store.
The bears stayed inside the van for about 20 minutes on Tuesday, said base store manager Shelly Deano.
The two hungry bears ignored banging on the side of the van that was aimed at shooing them away as they chomped on doughnut holes and other pastries, Ms Deano said.
“I was beating on the van and they’re not moving. I could hear them breaking open the packages and everything,” she said. “I was like, ‘They don’t even care.’”
Ms Deano said the bears ate six packets of doughnut holes and three packets of chocolate doughnuts.
The animals would not move until base security was called and sirens were sounded to scare them away.
They then wandered back into the woods.
Ms Deano said it is not unusual to see bears on base or around the store but nothing like this has happened before.
She said the delivery driver, who usually leaves his doors open when he visits the store, now closes them.
Ms Deano added that people who work at the military base are now more cautious, “We’re cautious when we come in, when we leave. When we take out garbage, we do it in pairs, especially if it’s dark,” she said.
Base spokesperson captain Lexi Smith said authorities on base “are aware of this and other wildlife situations throughout the past several months.”
“We urge the public to use caution to ensure you are protecting our wildlife and yourselves. Wildlife may be our neighbor, but they should not be attracted to our human food sources,” she said by email.