Those little black bugs flying around your houseplants most likely aren't "fruit flies." They're probably fungus gnats, and sand and patience make a good team to get rid of them.
Gardener's Guide to Winter Plant Protection
Fungus Gnats - How To Prevent And Remove From Your Grow Room - Hydrobuilder Learning Center
How to avoid Fungus Gnats on my herb garden plants
Kill Gnats On Indoor Plants Collection Discounts
Indoor Pest Control, Part 2: How to Get Rid of Fungus Gnats - Salisbury Greenhouse - Blog
How to Get Rid of Fungus Gnats and Save Your Houseplants: 11 Tested Methods - Mr.Houseplant
Eliminating Fungus Gnats: Treatment Options
Fungus Gnats! I'm losing this war against fungus gnats I've been fighting for months. Looking for advice. Details in comments. : r/microgrowery
How to Get Rid of Fungus Gnats in Houseplants, Organically! ~ Homestead and Chill
Sad day. Lost the fungus gnat larvae fight, had to remove these remaining 6 month olds to save them … :( : r/Lophophora
How to get rid of fungus gnats: for healthier houseplants
Fungus gnat fight - Produce Grower
Detecting and combating fungus gnats - Moowy UK
How to Get Rid of Gnats in Your Home