Sugar can make a sticky mess, but if ever this happened to you, you could still take the van to a mechanic to have the fuel line and engine professionally cleaned.

What you REALLY want to avoid is fine silt or other hard particular matter that remains in suspension in the gasoline rather than dissolving. Such crystalline particles can potentially pass through the filter into the engine and cause many tiny scratches, wearing down the precisely engineered moving parts and doing serious damage that would be very expensive to fix. Before adding anything to your fuel tank, be sure to check it for suspended fine particulate matter, especially if the container has been sitting unattended for a while!