Sugar content doesn’t matter at all, you can have 200g/day and be healthy assuming you get enough of the other nutrients as well.
What matters is your blood-sugar levels, soylent is fine in this regard.
But soylent has quite a bit of fat, so don’t go basing your diet on soylent or soylent plus high-fat (or very high protein) foods while drinking soda or other garbage. That’ll screw you up.
The only way it’d be a potential issue is if you’re severely diabetic already, have little to no movement, are losing weight, and recently ate high-fat/high-protein foods in the last couple days and you’re switching to soylent. That’d maybe have slight issues, but realistically anything but plain baked potatoes and vegetables would be worse and you’d be screwed regardless, so it’s not really worth bringing up.
tldr; if you have 5 servings a day you’ll be fine so long as you don’t have 4 of those servings at once and then have a steak with a side of disgustingly buttered Texas toast.