I think your post mixes two issues that should be kept separate: energy vs. electrolytes.
Electrolytes
I live in Japan and it is hot and humid. I don’t know where you live in China and what the climate is like, but you should definitely replace electrolytes. There are non-energy electrolyte tabs you can get (e. g. on Wiggle from various companies). They have essentially zero calories (I need to double check, but the ones I currently have from SIS have 5 kCal per tablet, I think). On the trainer I need to drink a lot more than outdoors. Indoors I currently average 1,4 l per hour (two large bottles). Outdoors, I can make do with 0,7–1 liter per hour. As you can see, it also depends on your sweat rate.
Energy
The other issue is energy. I try to consume 80–90 g of carbs per hour. At my FTP that doesn’t come close to replacing the calories I need even for a super easy 1-hour recovery ride like Lazy Mountain. Needless to say, it doesn’t come close to the calorie needs I have. So even if you want to lose weight, I don’t think fasted rides are the way to go.
If you don’t want to use drink mix, you can use e. g. gummi bears. That works very well and has the advantage that I can precisely monitor my calorie and sugar intake.
I found that if I fuel well with 80–90 g of carbs, I’m quite full after a ride. No big surprise, I drank 1.5+ liters of water and had as many carbs as my stomach can handle. After a shower, I take in a recovery drink. I don’t do this because I think it is really necessary, I do it because I like the flavor. I use SIS chocolate-flavored recovery powder and use milk instead of water. (I know I am not supposed to, but with water it tastes like chalk. With milk it is delicious.) You can go cheaper by simply blending milk with 1-2 bananas and some honey or maple syrup. You can add e. g. cinnamon or other things for taste. That will stuff you.