"There is no way you would be able to create money fast enough without sending the entire economy into a tailspin."
Based on what? The fed gave banks trillions in created money before they even informed the government of housing crisis. We don't know how much money they create in a typical year, because they are a private bank with no reporting obligation, we only know about that year because they were forced to turn over the information by government on a one off basis. We are currently at risk of deflation, which is dramatically worse than inflation with our fiat currency. We've just erased trillions of dollars in phantom debt through refinancing, and we are just beginning to feel the impact through slowing growth.
Taxation would have to play it's part, money generated at the fed tap is still a loan with some nominal interest but the dollars it is paid back with are worth less than the dollars borrowed thanks to inflation. I've proposed a UBI equivalent to a 40 hour workweek at $15/hr. That is $31,200. That requires $78 worth of interest at the current rate while inflation will devalue it a little more like $312 in the same period. Now say that goes to someone who makes that same amount currently, even if you don't tax the UBI itself but still factor it for determining tax bracket for the rest of the income, that will someone will have their remaining $31,200 taxed at a 10% higher rate, generating $3,120 in extra tax revenue. For the person this a very good deal, paying $3,120 for $31,200 is a no brainer while recouping 40 years worth of interest on that loan. As a nation we need to make up that $31,200 in economic growth at some point in the next 400 years along with covering interest to break even. If that individual by virtue of having another $28,080 to play with manages to be able to put 10% in their retirement account we'll get that value back in 10 years not 400.
It's actually a perfect marriage of conservative and liberal economics. You put free flowing cash in the hands of the people and this enables them to spend and invest that money creating economic growth. The additional inflation creates a built in (if small) tax on all existing money including billions sitting in a bank or held in a business by warren buffet using tax loopholes which is how we actually pay for it. Which means the wealthy can't merely sit on their laurels, they at least have to take greater risks leading to greater rewards to maintain their wealth. Enables greater investment by the middle class means the benefits of our corporations globalizing is better distributed among our population as our middle class is able to invest more and more in the stock of those corporations and owns a bigger piece of them. While jobs moved overseas the growing profits will remain here and offset that lost income.
It doesn't really matter how much you grow or shrink the number, the math works out the same we can float a massive number on UBI and it won't change anything.
Additionally, having a real and substantial UBI set at minimum wage levels will eliminate the need for the minimum wage. This would allow our food production and unskilled services to remain inexpensive while improving the lives of those who work there. Limiting UBI to existing citizens and their descendants would even allow us to easily legalize all the illegal immigrants and open borders without worries about disrupting food supply costs and job availability.