In reply to streapadair:
Why stop at 100CHF? Just take 1 x 1000CHF and call it good.
Most will now accept some form of electronic payment. In Switzerland we use Twint more than Apple pay etc, but I can't remember the last hut I went to that was cash only.
But also second the suggestion to just send them an email or call before. I would be surprised if you found a SAC hut guardian that won't speak English on the phone.