I don't think you can make them regrow.
I used to have quite thick eyebrows which I hated. Now they're quite sparse. I use a pencil. Don't do the 1970s thing of a single line, but lots of little strokes with a sharp light brown pencil.
Well I find that Rapidlash has made my eyelashes grow from very average to quite long. They do the same product for brows, cheapest on Amazon. It's not a make-up it's a potion you apply ever night. Took about 3 weeks to notice a change (by the way sparse brows can be a sign of underactive thyroid).
I've used it for a couple of years. If I stop for a month my lashes went back to normal length. It made a big difference to me as mine have only ever been medium and insignificant.
I think I might need some of that RapidBrow. Mine also used to be thick...and dark. I was a redhead with very dark brows. Age has caused them to disappear...*sob*.
Tilly the Rapidlash is a clear liquid that you apply along the lid at the roots with a fine brush like an eyeliner, it doesn't go on lashes at all. I only put it on at night after I've removed all make-up - it's a growth stimulant.