Help! My Christmas tree STINKS!

We were gifted a lovely fake Christmas tree in January that we’ve been storing in a musty cupboard (we had nowhere else to put it). Please note, the cupboard has no visible mould or damp. It just has a horrible old, stale smell.

Well, if it isn’t the consequences of our actions, we put it up and decorated on the 1st and it reeks of musty cupboard. We foolishly thought it might fade over the coming days. Nope. I’ve tried spraying it with white vinegar, with scented anti bacterial spray, with astonish fabric freshener… it’s masks it for a bit and then the smell comes back as strong as ever. I just lost it and started scrubbing the bottom branches with a solution of warm water, scented washing up liquid, laundry detergent and essential oil… it was pointless, I sniffed them when I was done and they still reeked.

Short of throwing the whole tree out, what can I do?!