Archies Jandals can be a great option for people with Bunion's and will likely be a far better option for you than wearing flat jandals shoes which offer no support.
It's important to be crystal clear, that once bunions have developed, you cannot change this, except with surgery. So nothing will change the fact that someone already has bunions, however, there are certainly things that can make them progressively worsen and these factors are often the things that you can change.
There are many different causes of Bunions, hereditary factors being a substantial one that you cannot change, however, one factor that you can change are wearing footwear with no arch support.
In flat footwear with no arch support, if you are predisposed to rolling in at the feet (pronating), then this squashes the big toe inwards every time your foot contacts the ground. Over time, this repetitive rolling in of the feet and subsequent squashing in of the big toe can lead to bunions.
While we cannot change the bunion that is present, reducing the rolling in of the foot through the arch support will help take stress off the big toe which will help prevent it from worsening and may also provide some pain relief if pain is present.
One additional benefit of wearing jandals for people bunions is that the foot may also benefit from not being held in tight constrictive shoes which can cause the big toe to bend in even further. As jandals are all open, then there is no constrictive pressure on the big toe.
So in summary, we cannot change the Bunions that are present, however, if poor foot biomechanics are contributing to the issue, wearing the right footwear is a vital ingredient in slowing their progression.