Worst case, I move the cash to a 2% interest rate bank account and let it sit there. Best case, there are other investments I can make now with that capital, and end up paying less overall for whatever I was buying because having the money has made me money in some other way. Lucky case, the company bankrupts and I don't end up having to completely pay for the thing at all.
Being also European, it is rare to be offered interest-free financing, and when you are, is because you are already paying a premium and could find the stuff cheaper somewhere else. But occasionally, some shops do have the cheapest price and still offer interest-free rates. I always take it, and have no idea why I wouldn't do that.