Don't use energy packs simply to level up. Using them for the sake of leveling is a waste since you are already able to level up off of a single energy bar. Additionally, if you are following this guide, do not use energy packs before level 100. Using them before level 100 is a waste, since it only takes an hour or 2 to hit level 100 following this strategy guide. To make full use of an energy pack, you need a lot of energy to make it worthwhile. If you aren't following this guide step by step and are just looking to be a better player, you can still use this same strategy to your advantage.
The best use for an energy pack is to stock up on Untraceable Cell Phones, Concealable Cameras, and Computer Set-ups. You need around 400 cell phones, probably around 500 or 600 concealable cameras, and 250 computer set-ups to master all the jobs. Computer Set-Ups are also used to obtain the highest defense armor (Falsified Documents), so you can never get enough of those either. The problem is, the "Rob an Electronics Store" job is one of the least efficient jobs in the game, making it very hard to collect these consumable items. However, with an energy pack, you will easily be able to level up off of doing an inefficient job like "Rob an Electronics Store". Therefore, your energy pack should be used to collect these consumable items. Just use all of your energy on robbing an electronics store, then use the energy pack, then do the same job until you level up.
Demote your Mastermind
When using an energy pack to collect items, the goal is now not leveling up, but collecting as many items as possible with your energy pack. For this reason, it is important here to come into a fresh level without any extra experience points. Additionally, you should demote your top mafia mastermind so that you can do the job more times. If this is confusing you, think of it this way. Let's say you are level 100, and you have 750 energy, and you need 1250 experience points to level up. With an energy pack, you'll have 750 energy + 937 energy for the pack to use for that level.. energy is not a concern when you have an energy pack. Let's say that the electronics store job gives 27 exp. You will be able to do the job 47 times before you level up. However, if you demote your mastermind, the job will only offer 25 exp. You'll now be able to do the job 50 times before you level up. That is 3 extra items that you will be able to collect from demoting your mastermind. It may seem insignificant, but it will definitely add up, especially at high levels! Don't forget to promote your mastermind when your energy pack is used up!
Step by Step process:
1. Keep your energy pack until you level up.
2. Get to a fresh level.
3. Demote your Mastermind.
4. Use all of your energy on robbing the electronics store (enforcer tier).
5. Use your energy pack when you are out of energy.
6. Rob the electronics store until you almost level up.
7. Re-promote your Mastermind.
8. You should do your most expensive job right before you level up so you can get a head start on the next level.
9. Continue leveling!