Yes you can drink beetroot juice on an empty stomach.
It's actually better to drink the beetroot juice on an empty stomach first thing in the morning because on an empty stomach the beetroot juice will be absorb much faster and easier than it would when your stomach is full.
So to reap the full health benefits of the beetroot juice you should drink it while you have an empty stomach.
Every morning I drink a glass of beetroot juice before I eat my regular breakfast and the beetroot juice gives me a lot more energy through the day and my health is better as a result.
Beetroot Juice is a good energy drink as well as a good drink to detox your body.