While it may seem straightforward, there isn't currently a way to update an Azure Spot Instance VM size in the Azure Portal.

As always, I fallback to the Azure CLI, which is far more powerful and flexible than the Portal.

Warning: the following process may cause a brief interruption and restart of your VM.  Additionally, if you use Ephemeral Disks, they will be wiped during the resize operation.

Steps:

  1. Ensure you are on the most recent version of the Azure CLI.  Older version do not support Spot Instances.
az vm resize \
  --name {VM Name} \
  --resource-group {Resource Group Name} \
  --subscription {Subscription Id} \
  --size Standard_D2s_v3
Command to Resize a VM (including Spot Instances)

Hint: if you are unsure of available VM names:

az vm list-vm-resize-options \
  --name {VM Name} \
  --resource-group {Resource Group Name} \
  --subscription {Subscription Id}
Command to list available VM Sizes

That's it.  Thank you for reading.  I'd love to hear your thoughts or any questions that you may have.