If you were a CEO of a company with break-even operations & you got a $20M investment, how would you develop a strategy to spend or invest this money?

The most professional way before injecting $M you have to implement quality process to define the problem root causes and its solution for each operation.

Then go to lean six sigma with a clear statement " best utilization of $M"  to find out the best recommendations.

Also, you must know the full details of current status balance sheet and financial statement  to get all company overview e.g. total sales, stock, cost analysis, expenses....etc. 

Al of these Quality, lean six sigma and B.sheet & Financial statement ......etc.  leads to an accurate strategy and achievable  plan.   

In order to develop a strategy you must first have a goal.  In general, a goal is not really a goal unless it is a SMART goal - Specific, Measurable, Achievable, Results-focused and Time-bound. 

In the real world, a company at break even is unlikely to obtain a substantial investment unless the goal for that investment is already agreed.  There are many possible goals - develop a new product, increase turnover, increase profitability, etc.  Which one is chosen will depend firstly on the investor, and secondly on the existing shareholders and the Board of Directors. 

Once the goal is clear, working out the strategy is often relatively straightforward.