How dangerous is it to drink one redbull per nightshift?

I've entered this bad habit of drinking one redbull per nightshift at around 2 am.

Basically I drink a cup of espresso before the nightshift starts at around 6pm and then one can of redbull at 2 am during breaktime. I've been doing this for the past 4 months and I know it can't be that healthy but how unhealthy is it really? If I don't drink anything I feel so tired especially because it's a physical job, I've tried coffee and chocolate but it doesn't help that much