Here's a table of Uber's funding rounds.[1] What's keeping Uber going is Saudi Arabia's sovereign-wealth fund, which put in $3.5 billion last summer. They also took on $1.15 billion in debt last year. That's real debt at 5% interest, not some convertible deal.
Bloomberg says Uber is losing $800 million per quarter.[2] Unless they can find a bigger sucker than the Kingdom of Saudi Arabia, they run out of money in 2018.
[1] https://www.crunchbase.com/organization/uber/funding-rounds [2] https://www.bloomberg.com/news/articles/2016-12-20/uber-s-lo...