I'm having a problem, during the tutorial you could use energy drinks without leaving the island you were exploring. Last night I had like 3 to 5 monsters to beat, all a higher level than my unicorn & it was at 0 health so 1 more defeat & we would have had to leave which I didn't want to do. So I had 2 energy drinks, went to my inventory & tried using 1, the unicorn I wanted to use it on wasn't even on the list as far as I could find. How do I use energy drinks from the island?

As far as I know you can't. 

Energy Drinks are to my knowledge a means to go to new islands once your pet has 0 energy. They're not meant to keep you on the island you're currently on.