Can you fill a creme brulee torch with lighter fluid?

Not usually.

Most creme brulee torches use pressurized butane gas as the fuel. This is the same as your regular BIC dollar lighter. It's the most common and cheapest, stored in aerosol cans.

But more expensive petroleum fluids, such as Zippo or other naphtha fluid commonly using in camping stoves, and gasoline are not compatible with a creme brulee torch.