For those players who haven't the Cooking Skill required to make Energy Drink X themselves and have not reached the Floating Chamber on Whale Island in order to be able to collect it from the various Twin Towers there, you can find Energy Drink X on the 3rd Floor of the Lava Ruins.
Energy Drink X is the most potent of the three Energy Drinks available in Rune Factory Frontier. Beyond that, however, it is required to complete Rosetta's 'Story'.
Sue shared this information after I had researched the various Treasure Chests on Floors 4 and 5 without ever finding Energy Drink X on either. It is the 3rd Floor that has a Treasure Chest that often contains the powerful restorative drink.
I explored the 3rd Floor after reading her comment and confirmed the location, as well as creating a detailed Walkthrough description here. What is truly ironic, however, is that this information IS included in my Screen-by-Screen Walkthrough of the Lava Ruins. I had not read the Bestiary and Caves Guide recently. Today, when I accessed the Guide in order to add the location of the E. Drink X to the 3rd Floor Walkthrough, I discovered that I had included it when I initially created the walkthrough.
In any case, here is a new detailed description:
Here are the directions:
From the Isolated Stairway, go west down the long stairway. If you take the Shortcut Stairway, go north, detonate the bomb that clears the fallen masonry and continue north to the same long stairway, then descend. Go south past the Mini-Golems and then west through the sliding door that leads to a small chamber FILLED with Summer Monsters. (This is probably why I avoided the room for the most part in the early days of my explorations.) There are two Monster Generators in this chamber, each of which spawns two Summers. All plant monsters have the power to inflict Paralysis. If you are wearing a Wristwatch, you will be protected from both Stun and Paralysis. A Luck Blade or Smash Blade protects against Poison and Seal. The two in combination therefore protect against all common status ailments.
If you are riding a Transport Monster, it probably is best to dismount and use a weapon against the pesky creatures to clear the room most quickly. Paralysis will slow down the Monster unless you have consumed food with a temporary FX of protecting against Paralysis attacks.
There are two Treasure Chests in this chamber. One usually contains Fire Crystal, Lv. 6 or an Orange. The other most often contains Energy Drink X but sometimes yields Ketchup I believe.
I will include a new section in the Bestiary and Caves Guide for players who are looking specifically for E. Drink X. I refer players to my Guides but when asked a question often do not have time to reread all the information I myself wrote about a game... A little section dealing specifically with this should be helpful.