It's really hard to give good recommendations without knowing your particular circumstance but here is the thought process I have gone through around the same issue.

First of all, I think the standard advice of get enough sleep, eat healthy, exercise and stay within a reasonable weight (15%-20% body fat - lower if you can manage it) will solve the physical aspect of the energy equation. If any of those are off balance for you, get those sorted out. It will help you immensely in all areas of your life.

I also will assume you have strong motivation for working on your side-project. If it's to hopefully launch your product, learn a new skillset or whatever, if the idea of working on it doesn't itch in your brain all the time then sort that out. I think if you don't have a strong internal motivation for working on your side project there is no way that you're going to spend one hour a night, let alone four to five.

I'll go with the idea that you're trying to build a software product (let's say some kind of SaaS). Come to peace that building the product cannot and will not have the momentum of a rabbit but will be the lowly turtle or the snail. Accept this and be ok with it.

I think the biggest factor of success when working on the side on something is planning beforehand. I believe to build motivation for working on the product in your free time you have to know that you are making progress and there is light at the end of the tunnel. Planning is a critical aspect of this. To achieve this, you have to put on your product manager/architect hat and really figure out what the feature set you are building needs to be for the MVP, how much of what you are doing is going to involve learning new tech and/or how much you can do with what you know.

If you can validate your idea beforehand in some concrete way it will automatically be a motivation booster. If you cannot, focus on the most basic MVP that you can go to market with and accept that it may go bust. From this a good set of development tasks can start to be developed. Put an estimate on each of these and try to come up with a rough enough of hours. Let's say it's a 1000 hours of effort. Now, you can break that down into a date based on how much you can commit.

In terms of how much you can commit, I think we all know ourselves best. I certainly can't work 4-5 hours on my side project on top of a full day of normal work. I also certainly don't view those people with any kind of admiration. I need time with family, to exercise, get enough sleep, hang out with close friends, to chill, etc. and those take time. For me, I can't neglect those things. Be true to yourself and look at your schedule. Be critical about it. Realistically, how much can you commit using the week as a guideline and not daily. Can you do 4-5 hours a week? Great, do that. Start with that. There is good possibility that you will increase your weekly hours once you see progress.

Assuming the 1000 hours and 4-5 hours a week, now you kind of have a target date that you can measure your progress. Take your high level development roadmap and start breaking it down to a point where you can start actual work. Break it down into steps. These can be coding, reading, design work, researching, whatever that involves the side-project.

Personally, for me, I use a simple markdown file, open in Vim with the following:

# Next Steps
[ ] Item one
[ ] Item two

# Completed

Date
[x] Item three
[x] Item four

Date
[x] Item five
[x] Item six

# Review as Needed
[ ] Task or design decision that is important but not relevant right now

# Defer
[ ] Task that was part of next step but for whatever reason is deferred. Reason is provided.

When I am working, I will move items to the the Completed and add new items in the Next Steps near the end of the work session. I found this is the simplest and completely ceremony free. I tried Trello and other sprint planning type tools and I'm not that type. At the end of the day, you need to start working on your side project. If Trello or some other planning tool works for you then use it. For me, I realized I was wasting more time with the tool versus doing real work. The simple file gives a great overview of how much I've already done and when I start working again, I just look at the first line in the Next Steps and get going.

I think personally what has been the most effective for me is to just start working on it with a plan in place. I know that it's going to be months before I reach my development goals but I'm ok with this. As long as I can say, that I made progress during the week however incremental, it was a good week.