I think hot soylent would be pretty vile, but maybe adding in some cocoa powder to the mix would be worth a try? I know some folks use cocoa to great success in the cold mixes.
This just comes down to your personal caloric requirement. If you’re a 200lb adult male through-hiking the Appalachian Trail with a heavy pack, you’re going to need a lot more calories than a 130lb college girl on a 10 mile day hike. You’d probably want anywhere from an extra 2000-6000 calories based on those two metrics for an eight hour day (4000-8000 calories, or 2-4 bags of Soylent).
I know a few long distance hikers but haven’t done more than a day or two myself, so I’m not sure how many hikers are actually packing and eating that many calories or if they’re usually running on a deficit. There’s a good chance that Soylent isn’t quite calorie-dense enough to want to pack four bags per day for a multi-day hike, but an actual hiker would need to weigh in on this. You can get a rough estimate from any number of calorie calculator sites; here’s a link to one - http://www.fitwatch.com/phpscripts/viewexercise.php?descr=backpacking%20with%20moderate%20load&mets=8.0
The pitcher holds 2 liters and it is tastiest when it is dilute, but you could probably trim that down a bit for a denser slurry if you want to save water and drink more calories faster. It’s less water than you’ll need to stay hydrated though, so that problem might just solve itself.
You could probably pull it off with a nice big freezer bag, but it wouldn’t be as good as a hard container. On the trail you might just be happy with any slurry, though, even a clumpy one.