Would it make sense to carry soda instead of water in respect to save weight
(you can carry less food because you have energy in your "water")?
No, for a variety of reasons (leaving out, as you say "other health related topics"): Sugar, powdered Gatorade, and many other water additives all weigh less than soda.
Soda comes in cans/bottles which you'll have to pack out.
You'll generally filter/purify at least some of your water anyways, so you're rarely carrying all the water you'll use.
In this case to replace soda with water you'd have to carry more.
In warmer weather, soda cans and bottles will start to smell pretty quickly unless washed out.
outdoors.stackexchange.com/users/127/Russell Steen
For a day hike, yes, it could make sense, if it's the type of day hike where you need to carry water rather than drinking from sources along the way.
It's really just a matter of what you enjoy.
If you enjoy drinking soda, bring soda.
Let's say we have a liter of coke and liter of water.
Both of them weight nearly the same.
However, the coke contains a lot of calories whereas the water contains none.
This is not quite right.
The coke contains some carbs, which are part of its weight and volume.
If you aren't a person who enjoys drinking coke, then you'd be better off carrying those carbs in some other form that you'd enjoy more.
It doesn't give you an advantage in terms of weight carried.
outdoors.stackexchange.com/users/2169/Ben Crowell
Let's say we have a liter of coke and liter of water.
Both of them weight nearly the same.
However, the coke contains a lot of calories whereas the water contains none.
The law of conservation of mass , tells us that the total mass/weight of a solution is equal to the sum of the masses of the solute and solvent.
So if you add 100 g of sugar (the solute) to 1000 g of water (the solvent), which is roughly the ratio of sugar to water in soda , the sugar water solution would weight 1100 g.
There is no such law for conservation of volume.
Sugar has a density of about 1.59 g/ml and water has a density of 1 g/ml.
When you add 62.90 ml of sugar (which will weigh 100 g) to 1000 ml of water (which will weigh 1000 g) the sugar will dissolve into the water and the total volume will change.
I am not sure how to calculate the exact volume (or density) of the solution but it will be more than 100 ml and less than 162.9 ml.
What this means is that there is no weight benefit of premixing the sugar and the water, but there is a volume benefit and possibly a taste benefit.
Since sugar has a relatively low caloric density (2.4 cal/g) compared to fat (9 cal/g)
you would be better off carrying fatty foods to eat with pure water.
outdoors.stackexchange.com/users/5836/StrongBad
From a fluid perspective - The energy density of most soda (non-diet types) is high enough to kick off a digestive system response for processing food, which requires fluids and oxygen.
In the case of dehydration or high levels of exertion, where fluid replacement is the aim this is undesirable.
Coke and energy drinks that contain Caffeine add a diuretic, meaning they are even less effective for hydration.
In these situations Soda is a bad choice (although infinity better than nothing) for fluid replacement.
As long as you are on a gentle hike with moderate temperatures, you will be able to maintain hydration with Soda.
If there is any chance of becoming dehydrated or needing to maintain high fluid intake to maintain hydration, Water is by far the most preferable option.
A better option than Soda is isotonic sports drinks, however, be aware that most items sold as sports drinks are not much better than soda.
Most of the modern ones contain way too much sugar and not enough salts and minerals, because true isotonic sports drinks taste a lot like watered down sweat and don't sell well at the convince stores.
All that said - (nearly) anything you drink is infinity better than something you don't like the taste of and won't drink.
If you would drink 2 litres of Coke over a days hiking vs sip only 200ml or water, take the Coke.
From a food/energy source perspective: Sugar is bad for hiking.
It gives you a short high then a massive crash.
Without careful management, this cycle can make an otherwise pleasant day one from hell, especially if you are not used to doing it.
Solid food is a better way to get energy
has you have a more accurate idea of what is going into your system, and you tend to take foods that provide better slow release, longer lasting energy.
Each person is different, so what does not work me may be perfect for you.
All I suggest is try it on a shorter easy trip and see if it works for you.
For me, first and last time I tried energy drinks on a trail, I spend the next miserable hour with stomach cramps and no energy - I'm sticking to water and isotonic drinks for my fluids.
outdoors.stackexchange.com/users/None/
I'll be brief.
100 grams of sugar and 900g of water when mixed still 100g of sugar plus 900g of water, not a miracle of 100g sugar and 1000g water concoction.
Mass preserving law, considering almost no nuclear or chemical reaction inside your Cola
(I'm not so sure about this hell mixture).
So, if you want fast calories at hike, take carbohydrates as the maltodextrins.
If you want the most light-weight calories, grab a pure fat.
outdoors.stackexchange.com/users/9403/Les
Let's say we have a liter of coke and liter of water. Both of them weight nearly the same. However, the coke contains a lot of calories whereas the water contains none.   Despite other health-related topics (teeth etc.) and personal taste, would it make sense to carry soda instead of water in respect to save weight (you can carry less food because you have energy in your "water")?
Carrying soda instead of water due to nutritional energy?
outdoors.stackexchange.com
<hiking><nutrition>
outdoors.stackexchange.com/questions/11682
outdoors.stackexchange.com/users/8060/OddDeer
From a fluid perspective - The energy density of most soda (non-diet types) is high enough to kick off a digestive system response for processing food, which requires fluids and oxygen. n the case of dehydration or high levels of exertion, where fluid replacement is the aim this is undesirable. In these situations Soda is a bad choice (although infinity better than nothing) for fluid replacement.  From a food/energy source perspective: Sugar is bad for hiking. you would be better off carrying fatty foods to eat with pure water. Solid food is a better way to get energy Solid, fatty foods and pure water are preferable. You would need to carry more soda than water.
Soda stimulates digestion and may dehydrate you. The sugar is bad for hiking and you'd need to carry more soda than water. Solid, fatty foods and pure water are preferable.