I need a vegan thickener that dissolves well and doesn't have any flavor. I tried tapioca flour the other day and it didn't dissolve very well and left a powdery mouthfeel. Cornstach is not bad. Arrowroot seems to work like cornstarch but it seems like you need more arrowroot to do the same job as cornstarch.  I'm specifically looking for answers involving personal experience with hot and cold beverages - not a list of thickeners I can find online. Hot chocolate and chai are two drinks that I've been doing with non-dairy milk but I would like a creamier, thicker mouthfeel like you'd get from whole milk or cream.   I'm aware of xanthan gum, agar agar and carrageenan, but they're all relatively expensive so I have not personally tried any of them. Personal experience with those would be cool. I really like this Bolthouse Farms cold chai protein drink, which is vegan and lists carrageenan as an ingredient, so I was thinking about trying to get some of that. Also guar gum? Cellulose gum? 
If you are talking about the Bolthouse Farms Vanilla Chai Tea, the problem you are running into is that its actually a blend of a plain chai tea and a lightly vanilla flavored soy protein blend. I have tried a few times myself to duplicate it and i came up with this...   I would make a good hot chai and mix it with vanilla soy protein powder and whisk it smooth. It was cheapest, tasted closest and i could adjust protein levels upwards without making it chalky. (also gave the desired mouthfeel you were describing)   Other than that:  Testing Vegan Thickeners(Pumpkin pie)     Arrowroot   This was my choice in the end. Arrowroot created the texture closest to a traditional pumpkin pie and had no discernible aftertaste or other negative effects. It's more expensive than egg replacer if you buy it with the other prepackaged bottles of spices, but go somewhere that has a bulk spice area, and it is totally cheap. If you like having the specially labeled 'Arrowroot' bottle (which I do) you can also buy the pricey bottle the first time and then just refill it from the bulk section in the future.         'Natural Desserts' Unflavored Jel   Wins 'Most custardy', with a crust around the edges, but not firm enough to remain intact when served. Still yummy and the smoothest choice. It would be better for a pumpkin pudding than pie. This is also the least common, and most expensive option. So it is not recommended, but I thought I'd still mention it as it was part of the process.     Egg Replacer   I've had some bad egg replacer baking experiences but this was not one of them! The texture was somewhere in between the arrowroot and Jel, so it could hold it's shape when served, but just barely. I think using any more than 2 eggs worth would leave an egg-replacey taste. Not sure how else to describe it, but if you've baked with it, you may know what I mean.  Best Binders and thickeners in a raw diet     Agar Agar     A gelatinous substance derived from red algae and is used in desserts throughout Asia.It can be used as a thickener in soups jellies and ice cream.     Coconut Oil   Made from cold pressed coconut meat.It is a raw naturally saturated fat containing medium chain fatty acids which the body can easily metabolize. It is used often in desserts but also as a skin moisturizer.     Cacao butter   Replaces butter in sweets and is also used in white chocolate desserts.     Dates   Great for use as a binding agent such as Christmas pudding in place of eggs.Blended with water they will both bind and sweeten.     Soy lecithin   Will act as a binder in sweets and cakes.     Flax seeds   Are rich in Omega 3 so are a good alternative to fish and can be used in soups and dressings as a thickener, or as a binder in cakes and burgers. 