Question

If D- and L- glucose are enantiomers, are D- and L-fructose not enantiomers?

Answer 1

What are you talking about? They ARE enantiomers.

Here, this source says so:

"D- and L-glucose are enantiomers, nonsuperposable mirror-image stereoisomers. Similarly, D- and L-fructose are enantiomers."

If two sugars have every horizontal `"OH"` and `"H"` pair switched, they are enantiomers.