I'm playing this after I saw your request for more detailed feedback, so I'll do my best to provide that. I played this through the ich.io app.
The title screen is quite ugly, specifically the text for "SUGAR", it doesn't mesh very well with the font used for "CRASH" or the buttons. I'd suggest reducing the number of colours used on the title screen overall. It's great that you included a guide on how to play. I would maybe try to explain it in fewer words, or at least break the text up into paragraphs. The "QUIT" button doesn't work for me.
The game (at least for me) only had a short playtime, which meant a lot of retries - so it was annoying to have to return to the main menu each time to begin again; a quick retry option would help.
The graphics are OK, they have a cute quality to them; they remind me of those play mats you would drive toy cars around on as a kid. There isn't a lot of variety in the buildings. There isn't much in the way of animation either, so the game feels very static. I think you could really commit to the cute art style and populate the town with people and buildings to match. You could also just go with it being all about sugar and fill the place with candy and that sort of thing. As is, the "POP" on the soda bottles is hard to read. Some kind of visual feedback when you get some soda would be nice, maybe a bit of screen shake when you crash too.
The UI is fine but I think the "time until crash" bar is a little small and you really have to take your eye off the action to check it. Some kind of visual indicator closer to the car would help, I think. Maybe the screen could lose colours and slowly shift to greyscale as you run lower on sugar (or just the car could become grey/transparent). I didn't use the controls display much, easier just to figure it out as it changed; I can see you need to include something like this though.
I liked the music, I thought it fit the game and its style well. The sound effects are very simple and there are no sound effects for the car.
The main mechanic, the changing controls, is good. I like games that use the controls in interesting ways. However, it is difficult and not everyone is going to like it, as there is also an element of frustration to it. The main incentive for replaying is to better your score, so a scoreboard would be nice. However, if it were a bigger game, then some kind of objective would add to the replay value (e.g. reach this place in X seconds, Kasper's suggestions too).
I see how it used the theme but it become "worse" to the same degree each time, so I don't think it nailed it 100%. If there were other disadvantages as you consumed more and more soda, I think it would use the theme better. Maybe the screen could start to jitter, a rapid heartbeat sound effect or other effects people associate with sugar highs/crashes.
I tried to go as far as I could in different directions and I never hit an invisible wall. Also, the roads varied so that I couldn't just go straight forever without hitting a building, so good work with the level wrapping and design.
The controls when reversing don't work like they usually would, specifically the left & right are swapped to what they should be.
Sometimes a soda would spawn directly where the car was, meaning you unexpectedly swapped controls. So you may want to check that there is no collision with the car when spawning a soda.
The download seems quite large for the size of the game; I'm not familiar enough with Unity to know how to reduce it though.