If you have archived photos from previous years' professional photo shoots you could set up a shootproof online digital gallery. Charge a small price per photo and they'll be emailed directly to the customer. Perhaps you could reach out to your photographers from past years to request them if they have them archived (and the right to use them however you want).
What about old concert DVDs. Use an app to rip them into a digital video file, and put them on Vimeo under a paywall. Even if you only charge $10 for access. Some might not have purchased the DVDs back then, and will appreciate getting to watch them. Some will have lost their copy. And some of your current families will just enjoy watching concerts from before their time - especially now that everyone is stuck at home.
Zoom private coaching for Singing, Acting, Performance or Dance.
"At-home-survival kits". Put together packs with stretch bands, dance accessories, dance theory print-outs etc. and sell them to your customers with free delivery. Pre-orders only so you don't have buy excess stock.
Heavily discounted uniforms and merchandise. Set up an online store on shopify or Facebook, or just do the sales manually in a post. You could offer a massive discount of 30% or something (making sure you're still breaking even). Better for the stock you have sitting there to be cash in your pocket at the moment.
Studio branded snuggies, blankets, pillows etc. We're coming into the colder months here in Australia, and the perfect gift item for isolating families right now would be a blanket. You could sell (pre-order only) studio branded blankets. And at the end of all this, they can even bring them to eisteddfods on cold days. Google "customised blankets" to find suppliers.
Set up a special guest Zoom "opt-in" workshop. Stephen Tannos is charging $150 for a Zoom session. You could run it as a workshop, and charge $15 per person. The first 10 would cover costs, the rest would be profit.
Offer a brand new "community class" on Zoom. Maybe it's a mums' dance fitness class, or a pre-school dance class for newbies, or a 10 to 14 years beginner Hip Hop. They don't have to mix in with your existing clients. You could set up a whole new class, and promote it on local community FB groups. No need to cap class sizes - price it to scale big. $5 per class, and keep it simple. Aim it towards people who don't already dance