Go to any retailer and buy any in-demand product with the same market value as what you want to buy. Sell it on Craigslist or similar for cryptocurrency using a new wallet. Buy whatever you wanted to buy, never use that wallet again. Alternatively, mine the cryptocurrency yourself, again using a separate wallet for each purchase.

The deanonymization comes from tying any transaction performed by a particular wallet to your identity and thereby deanonymizing all of the other transactions. Which doesn't work if the wallet only ever has two transactions and neither of them are tied to your identity.

That's assuming traditional chains. Privacy coins also exist.